Sunday
February 14, 2016

# Posts by jim

Total # Posts: 1,577

math 5th
Between 2 and 4 yards, and A multiple of 0.5. No integer can be the answer, because it wouldn't divide evenly into 24.5. The only two possibilities are then 2.5 and 3.5. Which is it?
October 30, 2009

Pre-Calculus
I think you mean 9 cos (pi * x /6) where x is the month number 0 through 11. And very neat that snswer is. It provides a low of 2 and a high of 20. Mind you, you might want to mention that your actual answer is: 1,000,000(9cos(pi/6) + 11) or 10^6(9cos(pi * x/6) + 11) to make ...
October 29, 2009

calc
It all looks OK to me, except from 1 to e^4 you should have your signs the other way around: ln(1+ln(e^4)) - ln(1+In(1)) ... =~ +1.60944
October 29, 2009

trig
Ask yourself this: 1. If x>0, is |x - 2| - |x + 2| positive or negative or zero? (or think of it as "is |x - 2| > |x + 2| ?" 2. If x==0, then clearly |x - 2| - |x + 2| is zero. 3. Now, the interesting one: what if x is negative? Then is |x - 2| > |x + 2| ?
October 28, 2009

physics 8th grade
If a woman hasa mass of 50 kg calculate her weight in neutons
October 28, 2009

math
Your first answer, y = x + (1/x), is absolutely right. I don't understand why you would think that a square would be involved. Bringing in the square makes it a completely different thing, and that's why you're getting different results on your graphing calculator...
October 28, 2009

Algebra
You can't separate the added parts and take the square root of each. (You could if they were multiplied, but not if added.) I will show a counterexample. You were looking at sqrt(x^2+1). Consider this example - let x=3, then we have : sqrt(3^2+1) = sqrt(9+1) = sqrt(10) Now...
October 28, 2009

Algebra I
You've got the 2w bit right, but you haven't followed through on your original equation. Divide 2w^3 by 2w Divide 6w^2 by 2w Divide 4w by 2w Put 'em all back together. What have you got now?
October 28, 2009

Math
To graphing a straight line: 1. Draw your axes. 2. Set x=0 in your equation to get the y-intercept: x + y = 1 0 + y = 1 y = 1 so we have one point: (0,1) 3. Set y=0 in your equation to get the x-intercept: x + y = 1 x + 0 = 1 x = 1 so we have a second point: (1.0) 4. Mark the ...
October 28, 2009

college
Assume you are performing the calibration step of Experiment 8 and you begin with 80 g of water at 20 oC and 80 g of water at 80 oC. After adding the two portions of water into your calorimeter setup and following the procedure outlined in the experiment, you determine the ...
October 28, 2009

chemistry
Assume you are performing the calibration step of Experiment 8 and you begin with 80 g of water at 20 oC and 80 g of water at 80 oC. After adding the two portions of water into your calorimeter setup and following the procedure outlined in the experiment, you determine the ...
October 28, 2009

math
You're welcome!
October 28, 2009

math
2y^2-y(3-2(y-4)-y) Get rid of the inner brackets: 2y^2 - y(3 - 2y + 8 -y) Multiply the y into the brackets: 2y^2 - (3y - 2y^2 + 8y - y^2) 2y^2 - 3y + 2y^2 - 8y + y^2 Now collect the terms together.
October 28, 2009

MATH/SCIENCE
Easha has the right idea. You need to get all the inputs and outputs into the same units. There's water entering the lake, and there's water leaving the lake. The numbers are just given in different units, which is common in the real world! There's nothing ...
October 28, 2009

MATH
In each of them, find some factor all the terms have in common. Take #2 for example: 5a^2 - 25a^3 Well, both divide by 5, so we have: 5(a^2 - 5a^3) but we can also take a^2 out of the expression inside the brackets: (a^2 - 5a^3) = a^2*1 - a^2 * 5a = a^2(1 - 5a) So the whole ...
October 27, 2009

math
I don't think those equations came out right.
October 27, 2009

Calculus
Just from looking at 2x^2+10x and that has to be zero - I'd try -5
October 27, 2009

math
1 inch =25.4mm. That is right. But when squaring, you have to square both the units _and_ the numbers, so 1 inch = 25.4 mm (1 inch)^ = (25.4mm)^2 (1^2) inch^2 = (25.4^2) mm^2 1 in^2 = 645.16 mm^2 Or think of it this way: Draw a 3-inch line. That's 3 inches. Now make a ...
October 27, 2009

programming language
OK, my conscience nags me about that double. To do it right, then instead of taking the lazy way of converting to doubles, and comparing, then: if your current smallest is, say, 13/6 and your new line is, say, 27/13 you should do the comparison by finding a common denominator...
October 27, 2009

programming language
One approach, simple but with a caveat or two: You need a double for "smallest absoulte ratio so far". Initialise it to something very big. As you take in each line, a) calculate the surface and the volume as two integers b) calculate the absolute ratio as a double c...
October 27, 2009

pre calculus
Think of it as two curves to draw. One starts at x just greater than 0, somewhere in negative y, passes through (1,0) and (2,3) and off to infinity at x=3. The other comes down from infinity at x=3, passing through (4,3), and just touches the x-axis at a turning point (5,0) ...
October 26, 2009

geometry
We can't answer without knowing more, like what s is, and whether s is a unit of length or of area.
October 26, 2009

Math
"maximum: 8, range: 6" gives you your minimum number, so pencil that in, and 8 at the other end of course to make your maximum. Now, if you know what mode and median mean, you should be ready to write in some 6s, and spread about the same number of lower digits.
October 26, 2009

Math
More like substitution. You already worked out the hard bit: 1.25x + 0.75y = 129.75 and Reiny pointed out that y = 117-x So you can replace (substitute) y in your equation: 1.25x + 0.75(117-x) = 129.75 and I'm sure you can see your way home from there.
October 26, 2009

math
You can do this with an equation. Let one of the numbers be x. Then the other is (70-x). And we know that x(70-x) = 1224 So -x^2 + 70x = 1224 and solve the quadratic from there. Another way is to list the prime factors of 1224, and guess your way through. Hint: 17 is a prime ...
October 26, 2009

math
I'm with Zava on the idea, but I think one of us dropped a sign along the way. And I'm not at all sure it wasn't me, so I'll check at the end. Dropped signs happen all the time. We have: x + y = 5 but we're also given what y is: y = x - 3 So we can just ...
October 26, 2009

math
please help, I have a test tomorrow and i don't get this. solve by substitution 1. y = x - 3 x + y = 5 2. 5x + 2y = 0 x - 3y =0
October 26, 2009

Math
Oops: that last line should have been = 6.3 * 10^9 of course!
October 26, 2009

Math
Yes, but "scientific notation" is often used when talking about powers of 10, like: 20000 = 2 * 10^4 This makes arithmetic with large numbers easy, since, following the rule above, all you have to do is add powers to multiply the factors of 10, like: (2.1 * 10^5) * (...
October 26, 2009

Math
I'll try to answer the case I think you're asking about. If I'm guessing wrong, do ask again. If you have something like x^2 * x^3 (x-squared times x-cubed) then you add the exponents: x^2 * x^3 = x^5 Similarly, in general, x^a * x^b = x^(a+b) With negative ...
October 26, 2009

Algebra 1
We know that y = mx + c where m is the slope, so the equation we're looking for has to be y = (1/5)x + c (or y = x/5 + c, which is easier to write n this board!) Now all we have to do is find c. We know that (5, -1) must satisfy the equation, do to find c: y = x/5 + c -1...
October 26, 2009

math
There are two things here. I think you dropped a sign along the way. You have y2 - y1 = 5-1 whereas I think you meant y2 - y1 = -5-1 When you fix that, you still need to find the y-intercept c to finish the whole equation.
October 26, 2009

maths
I answered this below, rather wordily. If there's something else I can explain, do ask.
October 26, 2009

scatter plots
OK, so you've plotted your points. The linear model assumption is that a straight line will go through them. It won't, of course, because they're not perfectly in a line, but the idea is to create a line that comes as close as possible to them, usually with the ...
October 26, 2009

algebra (check plz)
d) is not wrong, but it's not in its final form; you have a constant on each side. Subtract one from each side to get rid of the 1 on the LHS and you'll be finished.
October 26, 2009

math
You'd recognise it. :-) xy < 0 means xy is negative. When x is 1, what values can y have? When x is 5? pi? 1,000,000,000? When x is -1, what values can y have? If the product of two numbers, say x * y, is negative, what do you know about those numbers? One is p------- ...
October 24, 2009

math finals
15. and 16 are the answers I got for these questions for margie_o a few days ago, but I see I didn't agree with 18.8% then either.
October 24, 2009

Math Analysis
You probably took a wrong turn in what was included inside the fourth root. Easy turn to miss. :-) f(x)=(3/4)x^4 g(x)= ((108((3/4)x^4 + 2)-216)^(1/4))/3 = ((81x^4 + 216 -216)^1/4) /3 = ((81x^4)^1/4) /3 = 81^(1/4)x^(1/4) /3 = 3 x / 3 = x
October 24, 2009

math115
You can also do it by getting the prime factors of each: 15 -> 3, 5 24 -> 2, 2, 2, 3 44 -> 2, 2, 11 Now, your LCM must contain all the numbers from any one of those lines. Start by selecting any line, say 15: 3, 5 Now add anything else yu need from 24: 2, 2, 2, 3, but...
October 24, 2009

math115
15 ad 24 go into 360 evenly. Does 44?
October 24, 2009

equations
If they're sratring at x = 1 -> Y1 = 1997 , then x = 2 -> Y2 = 1998 then you can just count for a) and b) In the formula y = mx + c, m is the slope and c is the y-intercept, which should answer a couple of them. f) Once you've counted to 2018, just let x equal ...
October 24, 2009

College Algebra
You're right so far, which was the hard bit. Me, I'd just pull out the calculator at this point. I did, and got 67.2972 = 67.30 to 2 d.p. You can do it by = 29 * sqrt(sqrt(29)) or by log tables. I can't think of an especially clever way.
October 24, 2009

math
I get 1/(x-3)(x+3) = A/(x-3) + B/(x+3) 1 = (x+3)A + (x-3)B 1 = x(A+B) + 3A -3B -> A + B = 0 -> A = -B -> 3A - 3B = 1 -> A = 1/6; B = -1/6 = (1/6)(x-3) - (1/6)/(x+3)
October 24, 2009

Math
On what grounds do you choose d?
October 24, 2009

Math
No, c is not correct. In each of the other cases, what happens when x is the number given: a) 8/(10-90/9) b) x < 10/9, say 1/9 -> 8/(10-9/9) d) 8/(10-72) One of these three is undefined. Which?
October 24, 2009

Pre Calc still confused
Oops. Left off the last equals: 6.5/1.5 + 6/(1.5-4)+7/(1.5^2-4*1.5) = 0.066666...
October 24, 2009

Pre Calc still confused
OK. If it's (x+5)/x + 6/(x-4)=-7/(x^2-4x) then I agree with bobpursley's answer but the numerical answers aren't exactly -17/2 and 3/2; they're (-7+-sqrt(101))/2. If you plug 3/2 in, it'll be close but not zero. 6.5/1.5 + 6/(1.5-4)+7/(1.5^2-4*1.5)
October 24, 2009

Pre Calc still confused
Are the brackets right? I've tried (x+5/x)+(6/x-4)=(-7/x^2-4x), and (x+5)/x + 6/(x-4)=-7/(x^2-4x) and a couple of other permutations without achieving enlightenment.
October 24, 2009

algebra
We need a variable for the time. Let's call that t. And we can call the distance d. At t = 0 (1pm) you are 150 miles away, and as t increases, the distance decreases, so we need to subtract some multiple of t from 150 as we go. We need something that starts with d = since ...
October 24, 2009

math
Correct! Perpendicular lines have slopes that are negative reciprocals of each other. Thus perpendiculars of y = -(1/2)x + anything will have a form like y = 2 + something The two lines you specified are in fact parallel, because they have the same slope : (y = -x/2 + something)
October 24, 2009

math
It would!
October 24, 2009

Trig
I suspect you mean tan((m + n)/2) on the RHS
October 24, 2009

pre calc
Not sure you should go by me, because I took it down wrong the first time, but I got: x + 11/x - 4 + 7/x^2 + 4x = 0 Gathering and multiplying by x^2: 5x^3 - 4x^2 + 11x + 7 = 0 Does this makes sense to you in the context of your course?
October 24, 2009

programming
The confusion may be coming from trying to take in too many things at once. At root, all this is asking is for you to write a function to find a sequence like {8, 7} in a sequence like (1, 2, 3, 4, 5, 6, 7, 8, 9, 8, 7, 6, 5, 4, 3, 2, 1} - which is essentially the same process ...
October 24, 2009

Math
Which functions are exponential? A)3x B)3^x C)3x^2 D)2^-x I think that B and C are exponential. Am I correct?
October 23, 2009

Physics
As the time required to run up the stairs increases, the power developed by that person Increases, decreases, or remains the same. Is the answer decreases?
October 22, 2009

algebra
y = mx + c, where m is the slope and c is the intercept. You are told m, and you are told c, so all you have to do is plug them in.
October 22, 2009

algebra
y = mx + c, where m is the slope, and c is the y-intercept. You have y = -9x + (-7) So, thinking of it that way, what is the slope and intercept?
October 22, 2009

algebra
I didn't get it either, until I erad the question for the equation three times. It seems they're assuming that the life expectancy function plotted agaist the years since 1990 is a straight line, and I'm not at all sure you should assume that. Anyway, if we do ...
October 22, 2009

math 115
So plot your amount spent along the x-axis and your sales on the y-axis, and extend the line out to \$50. Nt much else we can help you with on this one.
October 22, 2009

algebra
he slope is just the difference in the ys over the differences in the xs. That is, when you move 1 in the x direction, how far do you move in the y direction. -4 isn't very far off, but it's not the exact answer: Your Ys are 13.4 and 2.1 Your Xes are -19.3 and -17.3 (...
October 22, 2009

math(rational functions application)
Call the speeds j and c. j - c = 100 -> j = 100 + c (100 + c) = 5c / 4 (from the "25% faster") Solve for c.
October 22, 2009

algebra
If I understand the question, 10, 12, 14 and 16 is not right. Is 2 * 10 + 16 = 96? Call the numbers a, b, c, d. We're really only interested in a and d. How much bigger is d than a? d = a + ? Call the unknown x. d = a + x Now, we know that 2a + d = 96 but we also know that...
October 22, 2009

corp. finance
It's tedious, but there isn't a useful shortcut. In year one, you add 13% of 5000 to the 5000, making 5650. Then you add 3500, making 9150. Then you add 13% to that, and then add another 3500, and go for another year @ 13%. And so on.
October 22, 2009

math
Would you fit a billion gallons of gas in your tank? Could you afford to? Would you stop to buy 1 thousandth of a gallon? The appropriate domain will be somewhere inbetween. You figure out what, based on your own good sense. Given your domain, the range easily falls into place.
October 22, 2009

Math
What is their combined speed approaching each other? The two cover all but 240km of the 3600. What is that distance? Divide the distance by the speed to find how long.
October 22, 2009

math
Imagine you're dividing the money into equal piles, and you're giving 2 piles to the first 4 piles to the second 6 piles to the third How many piles do you need? How much money is in each pile? Now, how much money does each get?
October 22, 2009

math
Imagine you start with \$1 (or \$1,000 if you prefer). How much would you have at the end of two years, under each of the schemes? For example, under the second, starting with \$1, you would have \$1 * 1.06 = \$1.061 at the end of the first year \$1.061 * 1.06 = \$1.12466 at the end ...
October 22, 2009

Pre- Caluculus
So what is the depth when full, when t=0? We want to make sqrt(100-2t) = half of that, which is 5. sqrt(100-2t) = 5 Square both sides. Subtract 25 from both sides. Now t is easy.
October 21, 2009

..
Mind you, the physicists proved it didn't exist back in 1887, so maybe you're imagining that!
October 21, 2009

..
Ineluctably ineffable, even.
October 21, 2009

english
Which is a theme of both “One Thousand Dollars” and “By the Waters of Babylon”? -Things are not always what they seem to be -If you do what is forbidden, you will pay the price. -Love can change the world -Life is not always fair.
October 21, 2009

Critical Thinking
A valid syllogism is: All A are B C is A therefore (since C is A and all A are B) C is B The non-syllogism above is: All A are B All C are B Therefore all A are B. Erm, no. Spot the difference. Here's one of the same form: All fish are animals All birds are animals ...
October 20, 2009

Algebra
Personally, I'd do those backwards from c, and I was taught to sketch graphs using a different method, so maybe someone else will be more in tune with your text. Anyway, following these steps: a) Start with a table of values. This function is most interesting in x [-3, 3...
October 20, 2009

Math
The commutative property of multiplication says that xy=yx. The commutative property of multiplication says that (x^2)+(y^2)=(y^2)+(x^2) That's all you need, though you can draw it out with substitutions if you want.
October 20, 2009

math algerbra
You'd need to post your work here for people to check, or at least tell us what kind of problem it is, to think of the best ways to check that kind of algebra.
October 20, 2009

math
Distributive property says, for example: 4 * 3.14159 + 5 * 3.14159 =(4 + 5|) * 3.14159 = 9 * 3.14159 that should give you the idea. And the second one is the same idea.
October 20, 2009

MATHS
There's the weight of the truck, and the weight of the papers. The weight of the truck doesn't change ever. The weight of the papers depends on how full the truck is. Let P be the weight of papers if the truck is full, tyhen: T + (1/2)P = 1762kg. T + (1/4)P = 1426kg. (...
October 20, 2009

Math Analysis
You don't multiply the co-ords, exactly. What you're scaling is the coefficients. But careful: f(-2x) is not -2f(x)! f(-2x) means might be a shorthand for f(g(x)), where g(x) = -2x. -2f(x) would be -2(3/4)x+2(3/2) =3-(3/2)x Your parabola is y=x^2, or f(x) = x^2 so 2f(x...
October 20, 2009

Math Analysis
OK. The original function is f(x)=(3/4)x-3/2 1. Yes, the function (3/4)x + 1/2 does pass through those points (-2,-1) and (2,2), as you can verify by plugging them in 2. You're right; there is no amplitude - but there is a slope! It doubles the slope, and the y-intercept. ...
October 20, 2009

math
Actually, what yu've written is a bit of both. Commutative is: 4 + 5 = 5 + 4 Associative is: (4 + 5) + 2 = 4 + (5 + 2) So 4 * (7*5) = (4*7) * 5 is Associative. but 5*7 = 7*5 is Commutative.
October 20, 2009

Math
We are given: (a) E = 2M and (b) E-3 = 3(M-3) So: 2M - 3 = 3M - 9 solve for M.
October 20, 2009

Math
In case you ever come back to this, I just saw MathMate answering the same question, but reading "6% compounded monthly" as "6% _per annum_ compounded monthly". This makes it a whole different question, and incidentally brings the interest rates back into ...
October 20, 2009

Math
P.S. Yes, this would mean that if you started with \$4,000, at the end of the year, you would have \$4,000 * 48482.72 = \$193,930,880 (and you took the measly 6% per month? :-)
October 20, 2009

Math
Right. It's not 1.03*365. It's 1.03 to the power of 365 aka 1.03^365 also written 1.03 with 365 written in superscript above and just to the right of 1.03. The power key isn't on all calculators. Scientific calculators usually have this function, and it's ...
October 20, 2009

Math
You have to take the 4000, and add 3% for the first day and then add 3% to your answer for the second day and then add 3% to your answer for the third day How do you add 3%? Multiply by 1.03. So just take your 4000 and multiply it by 1.03, and repeat the multiplication 365 ...
October 20, 2009

Math
Look at my second explanation. That takes it one step at a time. Each month, you have 1.06 as much as you had the month before, so at the end of the 12 months you have 1.06*1.06*1.06*1.06*1.06*1.06*1.06*1.06*1.06*1.06*1.06*1.06 as much as at the start. That is 1.06 to the ...
October 20, 2009

Math
Or you could so it this way: Start with one dollar. Add 6% to it. Add 6% to that. Add 6% to that. and so on for 12 months. At the end, you have \$2.01 (ignoring rounding). \$1 of that was your principal, so \$1.01 is interest paid during the year, which is 101%.
October 20, 2009

Math
(1.06^12 - 1) * 100
October 20, 2009

Math
And for b. yes.
October 20, 2009

Math
Think of it this way: After 1 month, you're 6% up, which is an extra 240. Next month, you get 6% of 4240, which is an extra 254.40, and you throw that into the pot. Next month, you start with 4494.4, and throw another 6% onto that again. Working through an example like ...
October 20, 2009

Math
It would be 4000 * 1.06^6, which is 5754.08 after six months.
October 20, 2009

Math
One reason I'm leery of this question is "6% compounded monthly". If that's supposed to mean 6% per month, which is what it seems to mean, it's a crazy interest rate, over 100% p.a. (3% compounded daily is even crazier! Waay crazier!) a. Anyway, in ...
October 20, 2009

CRT/205 critical thinking
I can't see how it could be a useful argument at any level. Even if you removed the species confounder it would reduce to "Withdrawal is a side-effect when going through the process using a blocker, THEREFORE there will be no withdrawal when not using the blocker.&...
October 20, 2009

CRT/205 critical thinking
I wasn't being sarcastic. The version I made up seems to me about equivalent to the original in its logical value. I was, I admit, hard put to come up with something as obviously wrong. Chemical effects on animals and humans (or other animals) are well known to be ...
October 20, 2009

CRT/205 critical thinking
Premise: Using a rider on a motorcycle, researchers recently have reported head injuries. However, to achieve this effect, researchers also caused a brick wall to jump up out of the ground in front of the motorcycle when it was moving at 60 miles an hour. Conclusion: if a ...
October 20, 2009

math
I'm guessing that it's a rectangle 15 across and 20 high, with a triangle on its left side, a right-angled triangle, 20 high and 15 at its base, with a hypotenuse of 25. And you need the area. The area of the rectangle is 15 * 20 = 300. The area of the triangle is half...
October 20, 2009

Math
This is really just like the other one - but simpler. You don't even need the brackets, assuming the question is written correctly: 4^n + 4n -4n^2 + 2^n - 2n (4n - 2n = 2n, sp) 4^n + 2^n - 4n^2 + 2n
October 20, 2009

math115
After doing a dozen of these answers, I can barely remember that 2+2=5 :-)
October 20, 2009

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