Tuesday

September 16, 2014

September 16, 2014

Total # Posts: 24,952

**Pre-Calculus/Trigonometry**

Uh, look at the table. 1 is the 5th entry in the x row 1.3 is the 5th entry in the f(x) row. So, f(1) = 1.3
*September 8, 2014*

**Math Proof**

sure could. But the argument is the same. Might as well work with what you were given, in this case at least.
*September 8, 2014*

**Math Proof**

Looks good. This is the method usually used to prove that √2 is irrational, but it works for any integer. You can find lots of proofs for that online. Look some up, and see how they use the same argument.
*September 8, 2014*

**Math**

clearly, the deduction will be .062*3260 + .0145*3260 It will be the same for all her paychecks, since her annual earnings will fall well short of the SS cutoff point.
*September 8, 2014*

**MATH HELP**

Now: 46 At the end of Day 1: 38 Day 2: 30 Day 3: 22 Day 4: 14 - order more Day 5: 6 Day 6: out of stock unless more has arrived
*September 8, 2014*

**Math Proof**

sum: Assume that it is rational. That is, if c = a/b, then a/b + x = m/n for some integers m and n. That means that x = m/n - a/b But m/n-a/b = (bm-an)/(bn), clearly a rational number, and x is irrational. So, if x is irrational, c+x cannot be rational. Clearly, cx must also ...
*September 8, 2014*

**math**

Assuming you mean (6x)^2 = (6x)(6x) = 36x^2 or, (6x)^2 = 6^2 * x^2 = 36x^2
*September 8, 2014*

**math**

D additive identity = 0 multiplicative identity = 1 a+0 = a a*1 = a for any value of a
*September 8, 2014*

**math**

hint. substitute to get 6x + 4(3-3x) = 0
*September 8, 2014*

**math**

since there are three values of x which satisfy the equation, there are three values for 2x+3.
*September 8, 2014*

**math**

(3,4/3)
*September 8, 2014*

**math 1 question**

powers first: 25-4/5+2 then multiplication and division, left to right: 25 - 0.8 + 2 then addition and subtraction, left to right: 24.2+2 26.2
*September 8, 2014*

**Math**

You have 26*1760+385 = 46145 yards since 1 meter = 1.0936 yards, that means you have 46145/1.0936 = 42195 meters When you get stuck, it's best to post your work -- that way we can help figure out where you went wrong. Just sayin'
*September 8, 2014*

**algerbra**

divide the second by 3 and you will see that they are the same line.
*September 8, 2014*

**phycis**

since mass * distance is the same, and the heaver mass only rises 1/6 as far, it is 6 times the mass, or 360N
*September 8, 2014*

**Math**

what is 1000000/100? It's 10,000 So, 10,000 CDs to each of 100 stores makes 1,000,000. 925,733 The 2nd 3 is just 3 The others are true
*September 8, 2014*

**math**

Hmmm. If the sides are in the ratio 4:5:6, then the sines of the angles are in the same ratio (law of sines) So, if sinA = 4x, sinB = 5x sinC = 6x arcsin(4x)+arcsin(5x)+arcsin(6x) = pi x = √7/16 A = arcsin(4√7/16) = 41.41 B = arcsin(5√7/16) = 55.77 C = arcsin...
*September 8, 2014*

**Math**

Id say f(x) = x h(x) = 4 f(x)
*September 8, 2014*

**math**

since the slope is the same, they are either parallel or the same line. I expect you can decide which. If parallel, no solutions, since they do not intersect. If the same line, there are infinitely many solutions, since any point on one line is also on the other.
*September 8, 2014*

**algerbra**

well, did you try any to see whether they are? (0,-1): -1 = 6*0-1? yes and so with the others.
*September 8, 2014*

**calculus**

∂u/∂x = 2x/(x^2-y^2) ∂u/∂y = -2y/(x^2-y^2) ∂2u/∂x∂y = ∂2u/∂y∂x = -2(x^2+y^2)/(x^2-y^2)^2
*September 8, 2014*

**math check answers**

I like all your answers. On #2, the markup based on cost is indeed 67%. The markup based on salling price is 40%, since the $100 markup is 40% of the $250 selling price. Could be they had a typo in the question or mixed up the answers.
*September 8, 2014*

**Math**

24(1.06)^(2013-1626) = $1.49*10^11 you may adjust it depending on whether the final year was an entire year.
*September 8, 2014*

**math - eh?**

sounds like a good deal. Is there a question in there somewhere?
*September 8, 2014*

**Algebra**

width: w length: w+11 so, 2(w + w+11) = 90 Now just solve for w, and figure the length.
*September 7, 2014*

**Algebra**

How approximate? Assuming you meant f(x) = -8x^2 + 2x + 2, f(-1) = -10 f(0) = 2 f(1) = -6 So, f(x)=0 somewhere in (-1,0) and (0,1). You can, of course, use the quadratic formula to get an exact answer and then approximate with as many decimal places as you wish. See http://www...
*September 7, 2014*

**math - eh?**

Heck, I can't even figure out what the string of digits and slashes even means! Maybe some parentheses around the terms will help. And two = signs? What's up with that?
*September 7, 2014*

**math**

If there are x lbs of 4.40 tea, then the rest (120-x) is 2.30 So, we need 4.40x + 2.30(120-x) = 3.00(120) Now just solve for x.
*September 7, 2014*

**Math**

If P(x) = x^2-4x, then since P(x) = x(x-4), it has two x-intercepts. Q(x) = x(x^2-4) = x(x-2)(x+2) so Q has 3 roots. x^2-ax = x(x^2-a) = x(x-√a)(x+√a) so there are 3 roots With 3 roots, there must be 2 extrema. x^2+ax = x(x^2+a) since a>0, x^2+a can never be ...
*September 7, 2014*

**Calculus**

x + y − 1 = ln(x^5 + y^5) 1 + y' = 1/(x^5+y^5) (5x^4 + 5y^4 y') y'(1 - 5y^4/(x^5+y^5) = 5x^4/(x^5+y^5) - 1 y' = ((x-5)x^4 - y^5)/(x^5 + (y-5)y^4) At (1,0), y' = (-4)/(-1) = 4 So, the line is y = 4(x-1)
*September 7, 2014*

**math**

18s^9 t^3 - 2s^9 t^2 can be factored into 2s^9 t^2 (9t-1) No idea how that can be evaluated to 9. I suspect there is something missing or garbled in the problem statement as shown.
*September 7, 2014*

**math**

341-115 = 226 341-120 = 221 So, any value between 221 and 226 will produce a number between 115 and 120. Or, using a compound inequality, we have 115 < 341-x < 120 -226 < -x < -221 226 > x > 221
*September 7, 2014*

**math**

You can figure out the mass of silver, then do all the conversions of mass to volume and back, or you can note that density(Al)/density(Ag) = 2.57 So, volume(Al)/volume(Ag) = 2.57 But, the volume of a sphere scales as the cube of the radius, so the radius scales as the cube ...
*September 7, 2014*

**math**

(12-2)p^7 = 10p^7
*September 7, 2014*

**algebra**

do it just the way to multiply 2-digit numbers: (23)(45) = (20+3)(40+5) = 20*40+3*40+10*5+3*5 = 1035 (7-6y)(7-4y) = 7*7 + 7(-4y) - 6y(7) - 6y(-4y) = 49 - 28y - 42y + 24y^2 = 49 - 70y + 24y^2
*September 7, 2014*

**algebra 2**

all polynomials have domain of all real numbers. All polynomials of odd degree have range of all real numbers, y=0 when x = ∛4 x=0 when y = -4
*September 7, 2014*

**Calculus**

You know the roots are x = (m±√(m^2-4))/2 So, if m<=2 there are not two real roots, so the total area is the same as the integral. If m>2, then you need to divide the integral into 3 parts, with the roots as the limits of integration. Reiny's solution of...
*September 7, 2014*

**Algebra**

You have two points on the line: (2,5) and (6,9). So, the line has slope=1, and its equation is c = m-3
*September 7, 2014*

**Geography**

∂2u/∂x∂y
*September 7, 2014*

**physics**

8.2m / 3.7m/s = 2.2 s
*September 7, 2014*

**physics**

just solve for a in 4100t - 17/2 t^2 = 9400t - a/2 t^2 a/2 t^2 = 5300t + 17/2 t^2 at^2 = 10600t + 17t^2 a = 10600/t + 17
*September 7, 2014*

**Quick question**

Just how would you propose we do asl in a text forum?
*September 7, 2014*

**Calculus**

clearly, each rectangle with upper-right corner at (x,y) has area a = xy Since y = 9-x^2, the area is just a = x(9-x^2) Not sure what you need to do with that information. The question is a bit vague.
*September 7, 2014*

**Math - Urgent**

(a) each term is -1/3 the previous term (b) each term is -4 times the previous term Just take the first two terms and find their ratio. Then check to make sure the same ratio is there for the next two terms, and so on.
*September 7, 2014*

**math**

the slope of the given line is -1/2 so, the slope of perpendiculars is +2 So, the line you want is y+12 = 2(x+7)
*September 7, 2014*

**Precalc**

try C(x) = 4.00 + 0.40⌈10x⌉ where ⌈z⌉ is the ceiling function (the least integer greater than z) For example, ⌈2.37⌉ = 3
*September 7, 2014*

**science/math (mean)**

I get 44.60333333... So, to three decimal places, that would be 44.603 However, since all the values are given to two places, I would have given the same answer you did.
*September 7, 2014*

**math**

6*22 + .18 * 2766.50 = 629.97
*September 7, 2014*

**math 8**

when multiplying powers, add the exponents. when raising a power to a power, multiply exponents. This is because, for example, (x^2)^3 = (x^2)(x^2)(x^2) = x^(2+2+2) So, you have #5: 8^3 * 8^7 = 8^(3+7) = 8^10 #11: (5/8)^3 = 5^3/8^3 = 125/512 #12: ((-2/9)^3)^5 = (-2/9)^15 = -2^...
*September 7, 2014*

**C programming**

Hmm. Looks good to me. Can you produce the results for a few values of x? Do you at least get cosh(0) = 1.0 ?
*September 7, 2014*

**math 12**

If C=D, C-D=0 and you cannot divide by zero.
*September 7, 2014*

**Math**

graphing what?
*September 7, 2014*

**physics**

658.1m / .03m/yr = 21936.7 yr
*September 7, 2014*

**physics**

in MKS units, .440kg * 98 mi/hr * 1000m/0.62mi * 1hr/3600s = .440*98*1000 / .62*3600 m/s = 19.32 kg-m/s
*September 7, 2014*

**Algebra**

correct. So, plug in either point. Using (-2,-3), you have -3 = (-2/7)(-2) + b b = -25/7 so, y = -2/7 x - 25/7
*September 7, 2014*

**Physics**

x(3) = 90m x(2) = 40m total distance: 50m total time: 1s avg speed: 50 m/s
*September 7, 2014*

**Math**

going down: 5/2 seconds going up: 5/1 seconds so, down+up = ?
*September 7, 2014*

**Geometry help**

Did you draw a diagram? AC = CD AD = AC+CD #1 ok #2. The calculation for x is just as in #1. AD = AC+CD = 7+7 = 14 #3. AD=AC+CD = 2(AC), so 6x-4 = 2(4x-3) x = 1 CD = 1 #4. As in #3, 12-x = 2(3x-1) x = 2 CD = 5
*September 7, 2014*

**AP Alegebra**

(√x+1)/(√x-1) multiply top and bottom by √x+1 and you have (√x+1)(√x+1) / (√x-1)(√x+1) (x+2√x+1) / (x-1)
*September 7, 2014*

**Law of Sines**

you have C and c and a, so you can find A using sinA/a = sinC/c Now, having A and C, you know that A+B+C=180, so you can easily find B. Then, use the law of sines again to get b: b/sinB = c/sinC = a/sinA
*September 6, 2014*

**Algebra**

reflecting through where? x-axis? y-axis? origin? Just to remind you, reflecting through x-axis: (x,y) -> (x,-y) y-axis: (x,y) -> (-x,y) (0,0): (x,y) -> (-x,-y)
*September 6, 2014*

**AP CAlc. AB**

since |sinx| <= 1, x^2 sin(1/x) -> 0 as x->0 So, all that's left is 3k. Doesn't really matter whether k is positive or not.
*September 6, 2014*

**Physics II**

What is the sign and magnitude of a point charge that produces a potential of -2.00 V at a distance of 3.00 mm?
*September 6, 2014*

**Calculus**

As a sequence, let Tn be the time taken to meet the car for the nth time. T1 = d/(b(c+1)) T2 = T1*b/(b(c+1)) ... Tn = d/(b(c+1))^n The sum of this series, with a = d/(b(c+1)) r = 1/((c+1)) is S = a/(1-r) = d/(b(c+1)) / (1 - 1/((c+1)) = d/bc That is the total flying time. So, ...
*September 6, 2014*

**AP Physics**

since time = distance/speed, 16.5/s + 16.5/340 = 2.90 s = 5.787 m/s
*September 5, 2014*

**AP Physics**

since the car is going 17 km/hr faster, and it is 0.130 km behind the truck, it will take 0.130/17 = 0.0076 hours You may want to express that in seconds :-)
*September 5, 2014*

**math**

that would be 21*16 + 18*20 = 696g
*September 5, 2014*

**math**

P = a-c = (a+b)-(b+c) = 49-13 = 36
*September 5, 2014*

**algebra**

y increases by 4 when x increases by 1. So, look for something like y = 4x+b Now, when x=1, y=0, so we end up with y = 4x-4
*September 5, 2014*

**algebra**

the height is the y-value at the vertex, where x = .658/.000814 Since y = x(.658-.000407x) the roots are at 0 and 1616.7 The bridge spans that distance
*September 5, 2014*

**algebra**

first rearrange the terms so you have 2x^2 + 2x - 5 = 0 Now just plug in the formula, where a = 2 b = 2 c = -5 x = (-2±√(2^2 + 4*2*5))/(2*2) = (-2±√44)/4 = (-1±√11)/2
*September 5, 2014*

**math**

using the same ratio, x/125 = 400/20000 x = 2.5
*September 5, 2014*

**Physics**

(a) 31.1t = 1/2*4.11t^2 t = 15.134 seconds Now use that t for parts (b) and (c)
*September 5, 2014*

**Physics**

see related questions below, and change the numbers as necessary. The key is to separate the 2.2 seconds into the falling time and the return time.
*September 5, 2014*

**math**

review scientific notation. There is a number and a power of 10. the number must be between 1 and 10. (Less than 10) When adding, the powers of 10 must be the same, just as you need a common denominator to add fractions. Then you can just add the numbers as usual, keeping the ...
*September 5, 2014*

**Math**

the chance it will not snow on a day is 3/5, so for two days, that is 3/5 * 3/5 = 9/25
*September 5, 2014*

**Math**

the ratio of 3.25in : 4cm for the short side is 3.25*2.54/4 = 2.07 close enough for jazz. Now use that scale factor to enlarge 4.6cm. Probably should express the answer in inches, as well, since that was the original frame size unit. Actually, you don't need the scale ...
*September 5, 2014*

**math**

just drag out your formula for the area of a circle: A = πr^2 In this case, r = 7 yd, so A = π(7 yd)^2 = 49π yd^2
*September 5, 2014*

**Operating Systems**

pages are accessed in the order acbd*a*c*b*d*e*f* Bad luck, that.
*September 4, 2014*

**math**

each photo is 2x2, so 2*60 = 120
*September 4, 2014*

**Math**

you can solve for x or for y. Which is of interest to you?
*September 4, 2014*

**math word problem**

300(1+.04)^5
*September 4, 2014*

**Pre-Calc**

As usual, draw a diagram. It is clear that if the height of the mountain is h, and the tower is at a distance x from the mountain, (h-180)/x = tan 21°35' h/x = tan 24°48' Eliminate x and you have (h-180)/tan21°35' = h/tan24°48' Now just solve for h
*September 4, 2014*

**Geometry**

I'd say 56 and 75 Maybe a bit more context would be helpful...
*September 4, 2014*

**AP Physics**

total distance: 7.7*4.5*60 + 2.8*2.8*60 = 2549.4 m total time: (4.5+2.8)*60 = 438 s so, avg velocity is 2549.4/438 = 5.8 m/s
*September 4, 2014*

**math help!!**

you have the difference of two squares: (a/6)^2 - (b/7)^2 So now the factoring is easy, right?
*September 4, 2014*

**math**

For the 4th test, 79+97+85+x = 4*85 so, x = 79 Then, for the 5th test, 4*85 + y = 5*(85+3) so, y=100
*September 4, 2014*

**math**

r = 6w+1 r+w = 50 so, r = 43
*September 4, 2014*

**math**

-10 -3 5 16 vs -3 5 -10 16 The second list would be unchanged if the new numbers were used.
*September 4, 2014*

**Math**

no way to solve for anything without an = sign
*September 4, 2014*

**Alhebra1**

3^2+(5+2)•4- 6/3 First, parentheses: 3^2+7•4-6/3 Next, powers: 9+7•4-6/3 Next, multiplication and division: 9+28-2 Finally, addition and subtraction: 35 As that is not one of the choices, I suspect a typo. Find it, fix it, and then follow the same steps.
*September 4, 2014*

**Math**

s = 2j+5 i = 4j s+j+i = 96 Now solve, using your method of choice.
*September 4, 2014*

**algebra**

8+3x(6-4)-1=13
*September 4, 2014*

**physics**

the height y of the ball at distance x is y = x tanθ - g/2v^2 sec^2 θ x^2 so, we want to solve for v in 110 - 9.8/v^2 * 110^2 = 0 v = 32.83 m/s
*September 4, 2014*

**math**

since the amount drops by 1/2 every T, the function is f(t) = (1/2)^(t/T) But, 1/2 = e^-ln2, so f(t) = (e^(-ln2))^(t/T)) = e^(-ln2/T t) = e^(kt)
*September 4, 2014*

**math rounding**

before we can do much, you have to fix "The value of the thousands digit is double that of the the thousands digit."
*September 4, 2014*

**Math**

review what supplementary angles are, then solve 10x-25 + 15x+50 = 180 Now that you have x, evaluate the two angles.
*September 4, 2014*

**math**

If there were already n tests, then if Diane scored d and Peter scored p, then with the current average of a, n*a + 97 = (n+1)(90) n*a + 73 = (n+1)(87) so, we can eliminate the a and have (n+1)(90)-97 = (n+1)(87)-73 (n+1)(3) = 24 n+1 = 8 n = 7
*September 4, 2014*

**algebra**

there is no solution. If you subtract 3x from both sides, you have 0 = -3 Is there a typo?
*September 4, 2014*

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