Friday

July 25, 2014

July 25, 2014

Total # Posts: 23,952

**geometry**

You may not have seen it like this, but A = C/π

**algebra**

-3° is 18° less than 15° At 3°/hr that will take 6 hours, and happen at 6 pm. midnight is 12 hours after noon, so the temperature then will be 15-3*12 = -21°C Note that since 6pm is halfway between noon and midnight, since the temperature dropped 18° by...

**science - not brilliant**

The greater minus the lesser is -39 - (-98) = -39+98 = 59°C

**math - typo?**

since the diagonals are equal, 2(5a+1) = 2(a+1) 10a+2 = 2a+2 a=0 I don't think so...

**maths - oops**

oops - heh heh 3w = 12 w = 4

**maths**

length+width=9, so w + 2w-3 = 9 3w = 6 w = 2

**math**

r = 6w+1, so since r+w=50, 6w+1 + w=50 7w = 49 w = 7 r = 43

**Math**

the circumference is 20pi meters. So, the linear velocity is 60pi m/min. angular velocity is 2pi radians per revolution, so 6pi radians/min you know the circumference. Divide that by 8 to get the distance between seats.

**new neutrich high school**

depends -- do you want to know how many calories are burned as time passes, or do you want to know how long it takes to burn a calorie?

**algebra**

(f*g)(x) = f(x)*g(x) = (2x^2+7)(x-6) So, now just plug in x=1

**Algebra**

assuming you want to find the value(s) of s that make the equation true, place everything over the common denominator of (s^2-1) and clear fractions. Note that s=±1 are excluded, because that would involve division by zero. 3(s+1) + (s^2-1) = 12 s^2+3s-10 = 0 and I gues...

**math**

every time she works one more hour, how much more money does she get? That is the slope of the line.

**Algebra**

$2/item is the slope

**Algebra**

15000(1+r)^2 = 16099.44 (1+r)^2 = 1.0733 1+r = 1.036 r = 0.036

**Math (Calculus)**

The volume of a shell of radius r, height h and thickness dy (because revolving around the y-axis) is 2πrh dx Now, our plane region is symmetric about the y-axis, so revolving all of it it is the same as revolving only the part for x>=0. o, we'll take the volume to...

**Math (Calculus)**

v = ∫[0,4] 2πrh dx where r=5-x and h=y = 2π∫[0,4] (5-x)(4x-x^2) dx = 2π(x^4 - 3x^3 + 10x^2) [0,4] = 64π check using discs: v = ∫[0,4] π(R^2-r^2) dy where R=5-(2-√(4-y)) and r=5-(2+√(4-y)) = π∫[0,4] (3+√(4-...

**Grade 12 Math**

(2a-5b)•(3a+b) 2a•3a - 13a•b - 5b•b 6 - 13a•b - 5 1 - 13a•b Now |a+b| = √3, so using the law of cosines to get the angle θ between a and b, we have 1+1-2cosθ = √3 cosθ = 1-√3/2 Now, we know that since a and b are u...

**math**

divide the volume by the base area to get (40*pi*3.5^2)/(28*22) = 35/44 pi or 2.5

**Calculus**

#1 ok #2 dy/y = dx/x^2 lny = -1/x + c y = e^(-1/x + c) = ce^(-1/x) so, (B)

**Algebra**

They all look fine to me, though it took me a while to separate the problems from your answers. If they were marked wrong, then the key is in error. As you have presented them, your answers are all correct.

**Math - Pleeeease**

once you start tossing in angles, you'd better have some trig. Either that or know some basic facts about certain right triangles. I assume you have heard of the Pythagorean Theorem. For this problem, draw a right triangle with the hypotenuse going from the starting point ...

**Math - Pleeeease**

well, since plane #1 is rising at 45°, its ground distance is equal to its altitude, or 5600. The 2nd plane coves less ground than its altitude. It is 8200 cos 60° = 4100

**Math**

1 = (x+6)/(x+6) so, the right hand side becomes ((2x-6)+(x+6))/(x+6) = 3x/(x+6)

**math**

if there were x cardholders, there were 744-x others. Now add up the money collected for each kind. 1.75x + 2.25(744-x) = 1477.50 1674.00 - 0.5x = 1477.50 x = 393

**math**

if $x at 7%, then .07x + .10(3x+44000) = 41770 x = 101,000

**math**

1000(1+.03/12)^(12*10) - 1000

**Math**

w+4w = 15 w = 3 so the length is 12

**math**

50000(1+.025)^10

**Algebra**

pi r^2 h = pi r^2 * 25 so, r^2 = 225 Now you can find r easily.

**Physics**

starting at height 0, its height at time t is -5t - 4.9t^2 If we fudge a bit and approximate gravity with 5 instead of 4.9, then we have -5t-5t^2 = -5t(1+t) at t=2, that's -30

**MATH PLS HELP CHECK ANSWERS**

#3 since y increases by 3 when x increases by 1, the slope is 3/1 = 3. Only one choice has a slope of 3. And, as Leo said, you can just plug in the x's and see whether the y's match! #4 ok #5 ok #6 looks like A to me. Did you even try the given points? #7 ok #8 ok You ...

**Algebra**

what you have written is an assertion, either true or false, depending on the value of x. I suspect a typo or an unfinished question.

**Math**

since the volume is 1, and the height is now 1/8, the surface area of the two bases is 8 v = Bh = 8(1/8)

**Math**

It must gain 12 hours, at 1/3 hour per day. Looks like 36 days to me. (Assuming an analog clock -- a digital clock will take twice that long.)

**Math**

that would be f(6)-f(5) plug and chug

**Math**

divide 360 into 5 equal parts. What do you get? 72. But, that is angle AOB, the vertex of an isosceles triangle. So, each of the base angles (OAB and OBA) is (180-72)/2 = 54.

**Math**

why bother with all those decimals? 4/16 * 7/16 = 7/64 4/16 * 7/15 = 7/60 The fractions are exact; the decimals are usually only approximate.

**Math**

yeah - you have trouble multiplying fractions?

**Math**

(a) 4/16 * 7/16 (b) 4/16 * 7/15 (b) is different because there are fewer marbles to choose from on the second draw.

**algebra 2**

If you mean I = nE/R + nr then I-nr = nE/R R = nE/(I-nr) If you mean I = nE/(R+nr) then R+nr = nE/I R = nE/I - nr

**Math Help!**

#1 since (a+b)^6 = a^6 + 6a^5b + ... if we let a=2x and b=3y we get (2x)^6 + 6(2x)^5(3y) + 15(2x)^4(3y)^2 + 20(2x)^3(3y)^3 + 15(2x)^2(3y)^4 + 6(2x)(3y)^5 + (3y)^6 64x^6 + 576x^5y + 2160x^4y^2 + 4320x^3y^3 + 4860x^2y^4 + 2916xy^5 + 729y^6 #2 Hard to show. The bottom-line entrie...

**Algebra 2**

#1 4*2*5 #2,#3: visit calc101.com and click on the long division button. It will show you all the details of polynomial division. #4: (x+3)(x+1)(x-2) Now just expand that. again, calc101.com has a button for polynomial multiplication.

**Algebra 2**

#1 we have (x^4)/4 − 3x^3 + (23x^2)/2 - 15x Fractions are a nuisance, so I prefer x^4 - 12x^3 + 46x^2 - 60x = x(x^3-12x^2+46x-60) Cubics are tough, but a little synthetic division shows that we have x(x-6)(x^2-6x+10) So, we know we have at most 3 extremes for a 4th-degre...

**math**

if the boat's speed is s mi/hr, then since time=distance/speed, we have 24/(s-4) + 24/(s+4) = 5 s = 11.05

**Math**

1/5 scale is a reduction

**Math**

well, the new base:height ratio would have to be the same: 38/12 = 19/6 So, since all the choices have h=36, which is 6*6, we need a base of 6*19 = 114 Looks like A to me.

**Math**

DA/HE = AB/EF, so 19/133 = 8/EF EF = 56

**math**

the heights are in the same ratio as the shadows, so h/5 = 24/10 h = 12

**Maths**

since y=x-k, x^2 + (x-k)^2 + 2x - 4(x-k) - 1 = 0 2x^2 - 2x(k+1) + k^2+4k-1 = 0 x = [2(k+1)±√(4(k+1)^2-8(k^2+4k-1))]/4 now, that looks like a lot of complicated stuff, but notice that it's really (k+1)/2 ± some stuff So, (k+1)/2 is the midpoint coordinate

**Math**

not in any general way. If f(x) = x then that's true. For other functions, it will be true only sometimes, but mostly never.

**Maths**

f(x) = 3x^2-6x+k = 3(x^2-2x) + k = 3(x^2-2x+1) + k-3 = 3(x-1)^2 + k-3 The vertex is at (1,k-3), so k-3 = 7 k = 10

**Maths**

since the variance is a measure of the absolute differences from the mean, shifting the mean by 14 and flipping the difference does not affect the variance. (B)

**Math**

if we let the vertex be at (0,0), y = 4(x/6)^2 = x^2/9 so, what's y(3)?

**math**

If we let one force be (7,0) then the other is (9cosθ,9sinθ) where sinθ = 0.4 cosθ = ±0.92 (7,0)+(8.25,3.6) = (15.25,3.6) (7,0)+(-8.25,3.6) = (-1.25,3.6) The magnitudes are 15.67 and 3.81

**Math**

n = d-2 n/d + d/n = 2 4/35 substitute in for n and we have (d-2)/d + d/(d-2) = 74/35 d = 7 so, n=5 check: 5/7 + 7/5 = (25+49)/35 = 74/35

**Math**

If we call the two forces u and v, then we have (using unit vectors), u = 15(3/5i - 4/5j) v = 4√2(1/√2i + 1/√2j) so, u+v = 13i-8j I expect you can find the magnitude of that...

**Math - Algebra**

if the distance from the edges is x, (8-2x)(12-2x) = 45 x = 3/2 So, the hole is 5x9 with area 45

**Math**

5P5 = 4! = 120

**math**

it advances 1 in/move after 12 moves it has advanced 12 inches. On the 13th move it covers the last 3 inches to complete the lap.

**Math - Algebra**

if the garden is x by y meters, x+y = 10 and xy >= 24 so, x(10-x) >= 24 x^2 - 10x + 24 <= 0 (x-4)(x-6) <= 0 since the parabola open up, the graph is below the x-axis between the roots. the roots are at x=4 and x=6 So, we need x <= 4 <= 6 Since usually the len...

**Math**

first, bequest is a noun. The verb is bequeath. I know, I know -- in English any noun can be verbed, but why bother, when there is already a perfectly good verb available? This is a sure sign of an incompetent attorney! Anyway, if the estate has $x, the red cat gets x/2 -1000 ...

**math**

c'mon, guy -- just substitute in the values: a▲b = 2a-3b, so 2▲(-3) = 2(2) - 3(-3) = 4+9 = 13

**alegbra - eh?**

If you mean N = 2500 + 100 - lna Cm >= 1 I still don't know what the letters mean The "equation" makes no sense anyway.

**ALGEBRA**

Thanks for fixing the typos. (Except for persisting in writing "in" for "ln") #1 From the context, I assume you meant ln3 - 2ln(9+18) ln3 - 2ln27 ln3 - 6ln3 -5ln3 -ln 243 or ln 1/243 #2 ln3 - 2ln15 ln3 - ln225 ln (3/225) ln 1/75 or -ln 75 #3 ln3 - 2(ln4 + l...

**calculus help**

recall that sinhx = (e^x-e^-x)/2 coshx = (e^x+e^-x)/2 so, sinhx+coshx = e^x 2e^x/e^x = 2

**algebra**

I assume you mean the function representing the height of the ball, such that f(x) is zero at x=3 and x = -5 How about f(x) = a(x-3)(x+5) = x^2+2x-15 Without further information, we cannot determine the scale factor. There are many possible parabolas with those two roots. I as...

**Math**

First, write the clues in math symbols: p = 3h a = h+16 a+h+p = 86 Now just start substituting to get rid of all the letters but one, then go back and calculate the other two values.

**algebra**

by definition, log_10(10^n) = n so, log_10(10^-4) = -4 Or, you can recall that log x^n = n*logx Since log_10(10) = 1, we again have -4*1 = -4

**algebra**

but 25 is not (1/5)^2 (1/5)^2 = 1/25 25 = 1/(1/5)^2 = (1/5)^-2 So, log1/525 = -2 loga = c*logb regardless of base. Using b for the base, log_b(b)=1,so logba = c

**Math 12**

I assume you mean 6 blue marbles, making 14 in all. Looking just at the blues, P(0) = 8/14 * 7/13 * 6/12 = 2/13 P(1) = 6/14 * 8/13 * 7/12 = 2/13 So, P(>=2) = 1-(2/13 + 2/13) = 9/13

**Math**

total bands: 185 P(pink) = 95/185 P(brown) = 90/185 I expect you can reduce the fractions.

**Geometry**

as a block of water, the displaced fluid is 36*18*0.25 = 162 in^3

**Algebra**

call the classes p,h,a. The clues are: p = 3h a = h+16 p+a+h = 86 now start eliminating values: p = 3h, so 3h+a+h = 86 a = h+16, so 3h + h+16 + h = 86 5h+16 = 86 5h = 70 h = 14 so, there are 14 art history students 42 psychology students 30 algebra students

**MATH**

hint 197g * 1atom/1.6601*10^-24 g = ? atoms

**MATH**

well, we all know that the sun is 93 million miles away. So you'd better get something like 9.3*10^6 186300mi/sec * 8.32min * 60sec/min = 9.300096*10^6 mi ta-da!

**Math 12**

2598960/78 = 33320

**Calculus, Riemann**

you need to revisit your posts and type in the functions. This copy/paste stuff is getting mangled. Use ^ for exponents, like x^2 for x squared. I can guess that 3 means ∑.

**Help w/ Math PLS**

Looks good to me. That was going to be my approach until I saw it so ably demonstrated...

**math**

14 total fruits, so P = 2/14 * 2/13

**MATH PLEASE HELP MRS.SUE!**

#1 C add 10 to get next term #2 C multiply by 2 for next term #3 D is the only possible choice, since the first two terms are -5,-3 #6 C These seem pretty straightforward. What ideas do you have on the rest? I don't want to do all your assignment for you...

**Calculus**

you figured how much will be there in 30 years if 32400 is deposited now. You want A(1 + 0.0801/12)^(12*30) = 32400 A = 2953.95

**math**

12/20 * 8/13

**Maths**

1st place to start would probably be the Pythagorean Theorem. Check it out.

**Math Question Please Help**

just put the words into symbols: m = s+2 h = s/2 r = m+s h = 2 Now start substituting since h=2, s=4 since s=4, m=6 now we know that r = 4+6 = 10 Don't know what the (12) at the end means.

**Math homework help**

so, go find the appropriate half-angle rule. What do you get? Just to get you started, for that θ in QIV, sinθ = -1/√2 cosθ = 1/√2

**calculus help**

Just use Lebniz's Rule: d/dx ∫[a(x),b(x)] f(t) dt = f(b(x))b' - f(a(x))a' d/dx ∫[cosx,sinx] ln(8+3v) dv = ln(8+3sinx)(cosx) - ln(8+3cosx)(-sinx)

**Calculus Help Please Urgent!!!**

With 4 divisions, the boundaries are 0 pi/8 pi/4 3pi/8 pi/2 So, the midpoints are at pi/16,3pi/16,5pi/16,7pi/16 So, we have 4 rectangles with width dx=pi/8, and heights 2cos^3(pi/16),... Add up the areas of the rectangles. I get 1.3330 To check, ∫[0,pi/2] 2cos^3(x) dx = ...

**math**

42

**Matrices**

dilation takes (x,y)->(2x,2y) translation takes (x,y)->(x,y+5) rotation takes (x,y)->(-y,x) So, combining, we get (x,y) -> (2x,2y) -> (2x,2y+5) -> (-2y-5,2x) So, just apply that to each coordinate. For example, (4,3)-> (-11,8)

**Algebra 2 help!!!**

just read off the product: -7x - 2y = 14 15x + 8y = -8

**Algebra help please!**

just add the respective elements: (6+3,-5+3) = (9,-2) Looks like (A) without the typo

**MATH**

just put the clues into symbols. if there are d dollars and h halves, d = h+132 d/h = 5/2 clearing the fractions, we have 2d = 5h now substitute in for d and we have 2(h+132) = 5h 3h = 264 h = 88 so, d = 88+132 = 220 the reward is 1/4 (88/2 + 220) = 1/4 (44+220) = 11+55 = $66

**Calculus (lim)**

x^3-6x^2+11x-6 = (x-1)(x-2)(x-3) So, for all x≠1, f(x) = (x-2)(x-3) as x->1, f(x)->2 since both factors are negative we need to show that for every ϵ>0 there is a δ such that f(x+δ)-2 < ϵ we can dispense with the absolute value stuff, si...

**Calculus Riemann sum definition etc**

I'm stumped by the cryptic symbols. Try the notation integral[a,b] x_i or xi for x sub i Whatever the function, the Riemann sum is evaluated by approximating the actual area with a set of rectangles, whose upper corners are points on the curve. Review your text, and maybe ...

**Trig**

using the logic of the solution to your previous post, try this one yourself.

**Trig**

since no QIII angles, a is in QIV and b is in QI sina = -7/25 cosa = 24/25 sinb = -15/17 cosb = -8/17 now just evaluate sin(a-b) = sina cosb - cosa sinb

**Trig**

since cosb < 0, b is in QII, so sina = 4/5 cosa = 3/5 sinb = 5/13 cosb = -12/13 Now just evaluate ain(a+b) = sina cosb + cosa sinb

**Algebra**

what's the trouble? They actually give you the equations to solve. What do you get for answers?

**trig**

depends on the positions of the two named animals. It will between 8*360 and 9*360 degrees

**math**

there are 201 numbers from 50 to 250. So, clearly, if 202 people are polled, at least two of them must have the same number.

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