Thursday

March 5, 2015

March 5, 2015

Total # Posts: 29,335

**math**

don't be put off by all the words. Just write each fact down as math. You have several amounts: a,b,c,e,g. 2a = 3c = 4e 5b = 6e = 8g Since the LCM(2,3,4) = 12, 2a,3c,4e must be a multiple of 12 Since LCM(5,6,8) = 120, 5b,6e,8g must be a multiple of 120 Now, if 4e is a ...
*January 13, 2015*

**Math**

the LCD is 4x. So, that gives you 2(x-3)/(4x) - x(4x+3)/(4x) = [2(x-3)-x(4x+3)]/(4x) = (2x-6-4x^2-3x)/(4x) = -(4x^2+x+6)/(4x) That's about as far as you can take it.
*January 13, 2015*

**Algebra**

#1 is an example of why we always set factored expressions to zero. If the product of several factors is zero, one of the factors must be zero. So, we must have one of the following: x^2+5 = 0 Cannot happen x^4+3 = 0 Cannot happen 100x^2-10 = 0: x = ±1/√10 100x^2+...
*January 13, 2015*

**Math**

correct!
*January 12, 2015*

**Math**

x + x+13 = 93
*January 12, 2015*

**Calculus**

Hmmm. I'd say it's 12 feet tall h = 12
*January 12, 2015*

**Math**

If $x is at 7.5%, then the rest (10000-x) is at 9%. So, add up the interest: .075x + .09(10000-x) = 849 ...
*January 12, 2015*

**Calculus**

oh, come on. f' is the slope of f. So, if f' > 0, f is increasing. f" indicates concavity. If f" > 0, the graph of f is concave up. Have you not read any of your text?
*January 12, 2015*

**Calculus**

in general, you cannot. You can, however, tell where f' is positive or negative or zero, or where f" is positive or negative or zero.
*January 12, 2015*

**Math**

Nope. (-2)^2 = (-2)(-2) = +4 Similarly, (-y^2)^2 = (-y^2)(-y^2) = +y^4
*January 12, 2015*

**math**

well, how many different ways can the dice turn up? How many of those have two 1's?
*January 12, 2015*

**MATH**

You have a point (15,450) and a slope (4), so the line should be p-450 = 4(x-15) I'd say (B) with a typo
*January 12, 2015*

**Math stem question**

the equation is correct.
*January 12, 2015*

**Math**

(50/x)*80
*January 12, 2015*

**Geometry**

since the arc lengths are the same, 90r = 60w So, r/w = 2/3 Since the areas vary as the square of the radii, R/W = = (r/w)^2 = 4/9
*January 12, 2015*

**Math**

3s+9c = 75 8s+5c = 67
*January 12, 2015*

**Math**

correct
*January 12, 2015*

**Algebra**

-2 ≤ d + 0.5 ≤ 4.5 -2.5 ≤ d ≤ 4.0
*January 12, 2015*

**Math**

so, did you use your calculator? What did you get? Just plug in the numbers as given you.
*January 12, 2015*

**Math**

If 6 are boys, then the other 12 are girls, so 12/18 = ...
*January 12, 2015*

**AP Physics**

all the kinetic energy is converted to potential energy, so 1/2 mv^2 = mgh or, h = v^2/2g
*January 12, 2015*

**math**

in hundredths, you have 8/100 60/100 70/100 Looks like they're already in order...
*January 12, 2015*

**Math**

well, just plug in t=3
*January 12, 2015*

**Algebra**

y = 1/3 x + 26/3
*January 12, 2015*

**Algebra**

just look up the point-slope form. You will see that the equation is y+2 = 1/2 (x-5)
*January 12, 2015*

**Math**

the speed (distance/time) is constant, so that means 5/37 = 25/m None of the choices matches that exactly, but it is easy to see that (C) is the same equation.
*January 12, 2015*

**Math**

If you really want to use the index as you did, just type 2root or 3root. "square root" always means index of 2.
*January 12, 2015*

**Math**

in that case, yes. If there is no index, 2 is assumed. Online, its usually better to say sqrt for square root cbrt for cube root 4throot, 5throot, etc. x^(1/n) for the nth root. It's too easy to mistake the desired index for a multiplier.
*January 12, 2015*

**Math**

the two temperatures are equidistant from their average, (10.4+7.6)/2 = 9.0 So, you have |t-9.0| = 1.4
*January 12, 2015*

**To: Anonymous and all others**

Well done, student! These are model posts of homework problems. The problem is clearly written, possible answers are given (optional, of course), and the student's answer is noted, along with an indication of the solution method. If actual work had been shown, that would ...
*January 12, 2015*

**math**

1/12 + 1/x = 1/4 x = 6 so, 6 hours for the friend.
*January 12, 2015*

**Math**

well, since 0.7 = 7 * 0.1, add up seven times 1/10 of 0.7. That is, divide the 0.7 into ten equal pieces, and add up 7 of them. divide 1/4 into 5 equal pieces. Add up 4 of them.
*January 12, 2015*

**algebra 2 help**

3|x+4| = 8 |x+4| = 8/3 so, x is 8/3 away from -4, either + or - A is the solution to |x+4| = 6 or 3|x+4|=18 B is the answer to |x| = 2 C is the answer to |x+4| = 15 D is the answer to |x+18| = 4 If you have a typo, the answer may be (A) And if you can't even spell "...
*January 12, 2015*

**chemistry**

does HCl dissolve Al2O3? It probably reacts with it, instead. If that's what you meant, then figure how many moles of Al2O3 you have, then check the reaction to see how many HCl it takes to react with one Al2O3. Then you will need that many moles of HCl. Convert that back ...
*January 12, 2015*

**Maths literacy, accounting, economics and business studies**

It certainly looks like good preparation. Especially the Accounting course ...
*January 12, 2015*

**physics**

Since there are 86400 seconds and 40030 km in the earth's circumference, the plane must travel 40030/86400 km. Assuming east-west travel at the equator. I assume that the question is ignoring the truly minuscule relativistic effects of such a slow speed. Also, what are the...
*January 12, 2015*

**Please check my Calculus**

all look good to me. No reason to be unsure on #2. Just the chain rule. If u = 3x, y=sec u y' = secu tanu u'
*January 12, 2015*

**Geometry**

min diam = 39.5 max diam = 40.5 area = pi d62, so plug in the values for d. Use the two values for d to get the dimensions of the box. The box's sides must equal the ball's diameter, right?
*January 12, 2015*

**Geometry**

they are the sides of the drum. Their area is circumference * height.
*January 12, 2015*

**Please check my Calculus**

#1 there are 4 points of inflection, so (E) #2 f = x^2-4x+7 f has a min at x=2, so C or D f(0) -> 7 f(3) = 4 So, (d) #3 is correct On stuff like this, it is always helpful to verify your calculations with a graphing utility, of which there are many online.
*January 12, 2015*

**Please check my Calculus**

#1,2 are ok #3: f' = 16/x^2 16/x^2 = (8-2)/6 = 1 x^2=16 x=4 in [2,8] So, (A) is correct
*January 12, 2015*

**Please check my Caclulus**

#1 ok #2 h' = (f'g-fg')/g^2 = (6*1-0*1/3)/1 = 6 So, B is correct #3 f' = -(x^2+2)/(x^2+x-2)^2 f' < 0 for all x So, (D) is correct
*January 12, 2015*

**math**

since you got -1 for your final answer, did you try it to see whether it works? How about y=0? (0+1)(0/(1-0)) = 0, not -1 assuming you meant (y+1)(y/(1-y^2)) (y+1)(y) / (1+y)(1-y) y/(1-y)
*January 11, 2015*

**math**

√(4/3) - √(3/4) 2/√3 - √3/2 2√3/3 - √3/2 4√3/6 - 3√3/6 √3/6 (C)
*January 11, 2015*

**college pre-calculus**

1 - 1/x = 2 - 2/x 1 - 1/x = 2(1 - 1/x) so, 1 - 1/x = 0 x = 1 so, 3 - 3/x = 3 - 3 = 0
*January 11, 2015*

**Math**

(a) You need 3 dimensions for volume. What you have is the area of one of the sides of the box. You need (100-2x)(100-2x)x = x(100-2x)^2 (b) You need the area of the base, plus the area of the 4 sides: (100-2x)^2 + 4x(100-2x) = (100-2x)(100+2x) (c) Now that you have the two ...
*January 11, 2015*

**physics**

If the gun were fixed in place, all the momentum would transfer to the bullet, which would then have momentum p = mv = .0551kg * 320m/s But, the gun will recoil, and we have to divide that momentum into two parts. So, if the gun has velocity v, the actual ground speed of the ...
*January 11, 2015*

**Calculus**

Since f(x) is not defined for x = ±2, any interval which includes either of those values will not satisfy the theorem. So, A,B,D are all out The only possible choice is C, which is ok, because f(-3/2) = f(3/2)
*January 11, 2015*

**Calculus**

Since we know nothing about f'(-4) or f"(-4), we can say nothing about the properties of f there. However, if the change in sign is inadvertent, and all the data are about x=4, since f"(4)=0, x=4 is an inflection point.
*January 11, 2015*

**8th Grade Geometry**

since the triangles are similar, we know that the angles A=X, B=Y, C=Z So, 2x+5y = 50 Y = 102-x C = 5x+y Also, the angles have to add up to 180. So, 50+(102-x)+C = 180 (2x+5y)+Y+(5x+y) = 180 Putting all that together, you can get 50+102-x+5x+y = 180 2x+5y+102-x+5x+y = 180 or, ...
*January 11, 2015*

**Calculus**

since f'(-2)=0 and f"(-2)>0, (-2,5) is a minimum. (f is concave up there)
*January 11, 2015*

**Area and Perimeter Word Problems**

area = 10x, where 2(x+10) = 50
*January 11, 2015*

**Area and Perimeter Word Problems**

what is 4700/94 ?
*January 11, 2015*

**Calculus**

well, you just find where f'=0 and f"≠0 for extrema f"=0 for inflection points f' = (3x-1)(x-3) so, f'=0 at x = 3, 1/3 f"(1/3) < 0, so f(1/3) is a maximum f"(3) > 0, so f(3) is a minimum f"=0 at x = 5/3, so there's an ...
*January 11, 2015*

**Calculus**

Check out the graph, and scroll down to information on the extrema at http://www.wolframalpha.com/input/?i=%28x%2B1%29%28x-3%29^2 I think you are doing things right.
*January 11, 2015*

**Area and Perimeter Word Problems**

well, 15*15 = 225, so ...
*January 11, 2015*

**maths**

the cross-section area of the water is πd^2/8 = 49π/8 So, the water flowing through is (49π/8 cm^2)(2m/s)(10min) = 2309 liters
*January 11, 2015*

**Calculus**

Or, you can plot multiple curves to compare them: http://www.wolframalpha.com/input/?i=plot+y+%3D+%3Dx^2%2F%28x^2%2B5%29+%2C+y%3Dx^2%2F%28x^2%2B20%29
*January 11, 2015*

**Calculus**

I believe the answer is (A), given the interval [-3,-½]
*January 11, 2015*

**Calculus**

or, you can think of it as 5x^2-(2xy)+7y^2=0 and since (2xy)' = 2y+2xy', that gives 10x-(2y+2xy')+14yy' and go from there.
*January 11, 2015*

**Math**

(x+2)^2 = x^2+4x+4 So, the first is clearly not the same (x-2)(x+1) / (3x+1)/(x+1) = (x-2)/(3x+1) So, except for the missing division symbol, the 2nd is ok.
*January 10, 2015*

**Maths**

You can set up the vertices PQRS as points on the x,y,z axes such that P = (0,0,c) Q = (0,b,0) R = (0,0,0) S = (a,0,0) Then the midpoints are: PS: (a/2,0,c/2) QR: (0,b/2,0) PR: (0,0,c/2) QS: (a/2,b/2,0) You can easily show that the lengths of those segments are equal. There&#...
*January 10, 2015*

**PreCalc**

In general, there is no way to solve anything of 5th degree or higher. So, unless you can pick out some rational roots or easy quadratic factors, you are left with graphical or numeric methods.
*January 10, 2015*

**Integrals**

Assuming you meant 3x+5y < 15, just plug in allowable integral values for y: y 1: 3x+5 < 15 2: 3x+10 < 15 I think you can solve those, right?
*January 10, 2015*

**maths**

I get 8+7
*January 10, 2015*

**maths**

At a rate of 5 m/min, after 36 minutes he has gone 180m. On the 37th minute he swims 20m and is done. No need to let go and float backwards again.
*January 10, 2015*

**maths**

I have no idea what a sequence and series pattern involves, but surely you do. Try fitting Reiny's solution into your framework.
*January 10, 2015*

**maths**

37 minutes see previous solution for the explanation.
*January 10, 2015*

**Math**

What, still no work of your own to start with? Try factoring the quadratics, and see which factors cancel. And lose all those stupid parentheses around each term. Use one set of parens around the whole numerator or denominator.
*January 10, 2015*

**math**

No, because 4/9 = 16/36
*January 10, 2015*

**Math**

I don't see any way to simplify either one, except maybe to lose all the parentheses in the first one.
*January 10, 2015*

**english n engg.level to find d error related**

I hope it's not in English...
*January 10, 2015*

**Algebra 1a**

the lines meet where the x- and y-values are the same (9x+27)/3 = (72-8x/9) x = -153/19 so, y = 288/19
*January 10, 2015*

**Math**

since 12 = (3/2)*8
*January 10, 2015*

**Math**

helps to read: since 12 = (3/2)*8
*January 10, 2015*

**math**

just set x=0 and see what y is. That is the y-intercept -- where the graph crosses the y-axis (where x=0). Better review the examples and graphs in your text.
*January 9, 2015*

**algebra**

factor out the (x-y): (x-y)(4(x-y)^2-1) Now you have a difference of squares: (x-y)(2(x-y)+1)(2(x-y)-1) ...
*January 9, 2015*

**math**

because 15 minutes is 1/4 = .25 hour. So, 1 hr 15 min = 1.25 hours distance = time * speed, as calculated.
*January 9, 2015*

**math**

he ran 1.25 * 12 km Now convert that to meters.
*January 9, 2015*

**Intro to computers**

there are 4 memory sticks, each with 1GB of storage.
*January 9, 2015*

**Math**

well, what is a when t=0?
*January 9, 2015*

**Math 6 help**

By the way, the scale is 1:9, not 1:9cm Or, you could say it is 1cm:9cm It could have any units, for example, 1cm:100m 2mm:3km etc. If there are no units, you can make them both anything you want, as long as they are the same. If one unit is given, the other must also be ...
*January 9, 2015*

**math**

She's also good with spelling. Just sayin' ...
*January 9, 2015*

**algebra 2**

Apparently you want to simplify the expressions. I'll do #19. y^3/y^2 = y z^5/z^3 = z^2 So, you are left with -yz^2 Try the others. What do you get? If in doubt, show your work.
*January 9, 2015*

**Algebra 1**

Surely by this point you know how to graph a straight line. Graph both lines, and you will see that they intersect at (5,75). Just put a nice dot where the lines intersect. You might want to have a larger scale on the y-axis than on the x-axis. Just sayin'.
*January 9, 2015*

**math**

Check the differences: 9,16,25 Those are perfect squares. The next square is 36, so the next term in the sequence is probably 57+36 = 93
*January 9, 2015*

**Math**

So, can you not just plug in some values and check the results? I'll show you my work if you'll show me yours... Note: Usually it's easiest to use -1,0,1 for checking stuff.
*January 9, 2015*

**CAL**

Come on. There's no way to have two relative maxima without either a minimum or an inflection point in between them. y' = 15(x^4-5x^2+1) y" = 30x(2x^2-5) y" =0 when x = ±√(5/2) So, f is concave down in (-∞,-√(5/2)) up in (-√(5/2...
*January 9, 2015*

**Deductive reasoning help**

From your question, I deduce that you haven't studied hard enough. This seems to be a pattern among students.
*January 9, 2015*

**Calculus**

How about just writing down a few terms? 5^1 - 5^0 5^2 - 5^1 ... 5^100 - 5^99 --------------- 5^100 - 5^0 If you want to do it the hard way, you could note that ∑(a-b) = ∑a - ∑b
*January 9, 2015*

**math**

since circumference is just a constant multiple of radius, the circumferences are in the same ratio as the radii.
*January 9, 2015*

**Multiplying Polynomials**

The order of distribution does not matter, since the associative property guarantees that the order of grouping does not matter, and the commutative property guarantees that the order of multiplication does not matter. You can drag it out by brute force: (t-1)(t+1)(t^2+1) t(t+...
*January 9, 2015*

**Math**

well, did you check 24 to see whether it satisfies the conditions?
*January 9, 2015*

**math(5th grade)**

Since there are 1440 minutes in a day, that would be 1000000/(25*1440)
*January 9, 2015*

**MATH**

Try plugging x=0. Does 7(-2) = 0+14? Do the same for #2. Does -10(-2) = 10-10(-1)?
*January 8, 2015*

**trigonometry**

well, you know that sinθ = 3/10
*January 8, 2015*

**Algebra 1**

The amount of oil should be twice the amount of lemon juice. y = 2x How much of each ingredient is needed to make 45 ounces of floor wax? x+y = 45
*January 8, 2015*

**Algebra**

http://www.wolframalpha.com/input/?i=solve+2x+-+y+%3D+1%2C+x+%2B+2y+%3D+3+
*January 8, 2015*

**6th grade math**

I parsed the words as 7 times as long as (x minutes more than a platypus)
*January 8, 2015*

**6th grade math**

7(x+10) = 112
*January 8, 2015*

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