Friday

November 27, 2015
Total # Posts: 35,831

**math**

S5 = 5/2 (2a+4d) S2 = 2/2 (2a+d) The sum of the last 3 is S5-S2, so we have S2 = 55-48 = 7 = 2a+d 2a+d = 7 5/2 (2a+4d) = 55 a=1, d=5 So, S3 = 3/2 (2+2*5) = 18
*November 27, 2015*

**Math**

the circumference is 8π ft. 2 ft per flower means you get 8π/2 = 4π ≈ 12 plants 20 seeds @ 2 ft/seed means a circle with a 40 ft circumference. So, the diameter is 40/π ≈ 12.75 ft
*November 27, 2015*

**Mathematics**

what is the formula for the ith term again? It seems garbled. There's a (3/n * floating around.
*November 27, 2015*

**Math**

y-intercept is where x=0. avg rate is (56-52)/(3-1) Looks like that would be 2 more hours. So, {0..5}
*November 27, 2015*

**Math (prob)**

the experimental results are his pass/fail of the test.
*November 27, 2015*

**Calculus**

let u = (x-r)^2 du = 2(x-r) dx dv = (1/r) e^(-x/r) dx v = e^(-x/r) ∫ u dv = uv - ∫ v du = (x-r)^2 e^(-x/r) - 2∫(x-r) e^(-x/r) dx Now do it all over again. Notice that the power of (x-r) has been reduced by one.
*November 27, 2015*

**math**

rotation of any multiple of 360/8 = 45 degrees. Also, a reflection across any of its 8 lines of symmetry.
*November 27, 2015*

**Math**

T(x) = 45 - x/300 (300,1) is not a point on the line. x has to increase by 300 for T to drop by 1°. Thus, (300,44) is the point you are after.
*November 27, 2015*

**math**

If there are x large prints, then there are 2x small prints. To break even, he needs 20*2x + 45*x = 510 I think you can now easily answer all the questions. Most of them don't even depend on the number of prints sold.
*November 27, 2015*

**math**

(A): the circle has a circumference of 8π feet. If the seeds are at least 2 ft apart, then at most 8π/2 = 4π ≈ 12 seeds may be planted.
*November 27, 2015*

**trigonometry**

since X is the foot of the altitude, any triangle with X as an angle will be a right triangle.
*November 27, 2015*

**trigonometry**

3-sided
*November 27, 2015*

**Trigonometry URGENT!**

amplitude is half the distance between the extremes. In this case, (125-99)/2 = 13 The midline (where sin(x) = 0) is (125+99)/2 = 112 The period is twice the time from max to min, or 28*2 = 56 So, we're looking at something like y=13 sin(pi/28 t)+112 Now for the phase ...
*November 27, 2015*

**Tamae**

220 * .05 = ?
*November 27, 2015*

**Math calculus**

see related questions below
*November 27, 2015*

**Integral Calculus**

if you set u = arctan(x), you have u du I expect you can handle that...
*November 27, 2015*

**jabu**

100 km/hr = 27.78 m/s v = √(2as) 27.78 = √(100a) a = 7.716 m/s^2 That is the minimum acceleration which will do the job. There is no maximum value.
*November 27, 2015*

**Math**

If the markup is x%, then (1+x/100)*.84 = 1.12 x = 33.33% = 1/3 1200 * 4/3 = 1600 check: 1600*.84 = 1344 = 1200*1.12
*November 27, 2015*

**Precalculus ????**

23 is the maximum hours, but you want the maximum temperature. sin(x) has a maximum of 1 5sin(x) has a max of 5 5sin(x)+19 has a max of 24 It appears there is a typo, since 24 is not a choice.
*November 27, 2015*

**math**

You have 1-2 + 3-4 + ... + 99-100 = (-1) + (-1) + (-1) ... + (-1) (50 times) = -50 Naturally, the 2nd sum is then +50
*November 27, 2015*

**math**

one step at a time... 11/15=(1/a+(b/c+(d/e+f))) 11 = 15(1/a+(b/c+(d/e+f))) 11 = 15/a + 15(b/c+(d/e+f)) 15/a = 11 - 15(b/c+(d/e+f)) a = 15/(11 - 15(b/c+(d/e+f))) Now for b: 11 = 15/a + 15(b/c+(d/e+f)) 15(b/c+(d/e+f)) = 11 - 15/a (b/c+(d/e+f)) = 11/15 - 1/a b/c = 11/15 - 1/a - (...
*November 27, 2015*

**math**

If there are n survivors, there are 5n meals. After 2 days, 2n meals have been eaten, leaving 3n Then the 3n meals lasted the n-4 survivors 5 days: 3n/(n-4) = 5 Now just find n
*November 27, 2015*

**math**

list the powers of 2 and their remainders: 2^1 2 2^2 4 2^3 1 2^4 2 2^5 4 2^6 1 ... you can see a pattern. So see how many times the pattern is repeated in 1000 powers of 2, and how many powers are left over.
*November 27, 2015*

**Precalculus**

no ideas of your own to provide? These two problems are really the same thing with different numbers. As you might imagine, the trick is to come up with a function you can analyze. So, on the first one, if we are starting at the midline, then since sin(0) = 0, we expect to ...
*November 26, 2015*

**Math - PS**

skip that middle section. It was a blind alley I forgot to erase. Cool problem. I had to try several things before I hit on the right trick to convert all the sums to products.
*November 26, 2015*

**Math**

sin2x+cos2x = √2(sin2x * 1/√2 + cos2x * 1/√2) = √2sin(2x+π/4) so you have [√2sin(2x+π/4)+1]/[√2sin(2x+π/4)-1] = [√2sin(2x+π/4)+1]^2/(2sin^2(2x+π/4)-1) Now, using sum-to-product formulas, √2sinu+1 = √...
*November 26, 2015*

**maths.augusco**

1/5 : 3/10 : 7/1 = 2/10 : 3/10 : 70/10 = 2:3:70 There will be some pieces in the mix, as 75 does not divide 720 I suspect a typo. Fix it, and you will see a better division of apples.
*November 26, 2015*

**discriminant**

24
*November 26, 2015*

**c programming**

what is the difficulty? Do you have trouble with I/O? Don't understand arrays? Don't understand functions? Have you worked out pseudo-code that takes the necessary steps?
*November 26, 2015*

**Programming**

well, just follow the loop. On entry, count=1 next iteration: count steps up by 2, so count=3 next iteration: count=5, so exit so, the output is 1 3
*November 26, 2015*

**Pre Calculas**

In fact, ln56/ln7 = log756
*November 26, 2015*

**math**

true
*November 26, 2015*

**calculus**

The first step is just to expand the polynomial: e^2t + 2 + e^-2t Now integrate each term. Or, remember that your function is just (2 cosh t)^2 = 4cosh^2(t) now use the half-angle formula for hyperbolic functions, and you will get the same answer. Hmm. I guess just expanding ...
*November 25, 2015*

**math**

since time = distance/speed, 4/(x-2) = 12/(x+2) Now just find x.
*November 25, 2015*

**math**

see related questions below.
*November 25, 2015*

**maths**

1/3 * 3/4 (1 is not prime)
*November 25, 2015*

**Algebra**

the growth after t hours is 1.036^t so, find t where 1.036^t = 2 t log1.036 = log2 t = log2/log1.036 = 19.5986
*November 25, 2015*

**Geometry**

If the answer was (2,5), the line of reflection was y=4. That, or A=(-3,-3)
*November 25, 2015*

**Geometry**

(-3,3) -> (2,3) -> (2,-1) or, (-3,3) -> (-3,-1) -> (2,-1) typo?
*November 25, 2015*

**Algebra**

exclude values where the denominator is zero. So, where is (k+7) = 0?
*November 25, 2015*

**math**

-sin10°
*November 25, 2015*

**just checking(:**

Bzzt. But thanks for playing It is b) -2 -4y = 8x y = (8/-4)x = -2x
*November 25, 2015*

**Algebra 1 Honors**

2.50 + 0.35(15.75-1)*4 = $23.15
*November 25, 2015*

**math**

it occurs where d/dx(R-C) = 0 I get a maximum profit of 3992.81 at x=2875
*November 25, 2015*

**Trig**

This is not an identity. It is an equation to solve. cos 2x = -.3 cos 72.5° = 0.3 But, we have -.3, so 2x is in QII or QIII 2x = 107.5° or 255.5° x = 53.75° or 127.75° You can also add 180° to each of those, since cos(2x) has period of pi. That will ...
*November 25, 2015*

**math**

clearly, y=x
*November 25, 2015*

**science**

what is the speed of sound at 25°C? If that speed is s, then If the cliff has height, it hits the bottom at time t, where 4.9t^2 = h. So, h = (8-√(h/4.9))*s Plug in your speed s, and find h.
*November 25, 2015*

**math - eh?**

Better read your question. It is gibberish.
*November 25, 2015*

**math**

18 * (32/72) 30 * (8/12)
*November 25, 2015*

**Math**

true, false if x has powers, it is a polynomial. If x is the power, it is an exponential, as in e^x polynomials have constant powers of a variable. exponentials have variable powers of a constant.
*November 25, 2015*

**Pre Calculus**

for any positive real a, y = a^x always goes through (0,1), so y = 4a^x always goes through (0,4) y = a^x + 3 also goes through there. y = h*a^x + k too, if h+k=4 negative powers also work.
*November 25, 2015*

**Algebra**

If x hours at 57 mi/hr, then since distance = speed * time, 57x + 56(4.5-x) = 254
*November 25, 2015*

**Geometry**

yes.
*November 25, 2015*

**Calculus 1**

You can see a nice graph with grid lines here: http://rechneronline.de/function-graphs/ You may have to adjust the y scale some so it fits. You can use that to estimate the area. I'm sure you can then evaluate the integral.
*November 25, 2015*

**derivatives**

is that (cos t)^2 or cos(t^2) ? Then express t as functions of x and y, and you have dy/dx = (dt/dx) / (dt/dy) then you can use that to get the 2nd derivative
*November 25, 2015*

**electron theory and ohms law**

ummm. E = IR ? This time find I.
*November 25, 2015*

**electron theory and ohms law**

E = IR = 6.4 * 20
*November 25, 2015*

**math**

average cost is (1/3 x^3 – 18x^2 + 160x)/x = 1/3 x^2 - 18x + 160 marginal cost is x^2-26x+160 so, where is 1/3 x^2 - 18x = x^2 - 26x ?
*November 25, 2015*

**Algebra II, part 2**

#6. Surely by now you can do this... #7. b^2-4ac = 9+4*2*18 #8. 3√-3 = 3√3 i #9. Multiply top and bottom by conjugate: 8(3-2i)/13
*November 24, 2015*

**Algebra II**

#1. x^2 has negative coefficient. downward #2. (5/2)^2 #3. hint: 15+1 = 16 #4. does not factor. Did you mean +2x? #5. shift left 2, scale vertically by 1/3, shift up 5
*November 24, 2015*

**algebra 2**

Well, I see 2x^2+3x+1 and 3ay^2+9a If you want to factor them, then you have (2x+1)(x+1) and 3a(y^2+3) Other than that, I'm not sure what you want to do with them.
*November 24, 2015*

**Trigonometry**

#1. no calculator? It will be in 1st quadrant. #2. how long is the court? The angle is x where tan(x) = 2.44/(court length)
*November 24, 2015*

**Math**

so, if the width is w, 2(w + 2w) = 126
*November 24, 2015*

**Algebra 2**

y = (x-10)(x-4) I expect you can take it from there, no?
*November 24, 2015*

**Math**

yep.
*November 24, 2015*

**Math**

the range is the set of 2nd elements of the pairs.
*November 24, 2015*

**Calculus III**

Looks ok to me
*November 24, 2015*

**Physics**

F = ma = 80kg * 9.8 m/s^2 W = Fd = F * 6m P = W/s = W / 15s P = 80*9.8*6/15 = 313.6 W Now you can figure the % eff.
*November 24, 2015*

**MacArthur physics**

height: s = 4.9t^2 speed: 9.8t range: 20t
*November 24, 2015*

**Math**

cool. nice and wavy.
*November 24, 2015*

**arvind mahila college**

T7/T4 = r^3 = (8/9)/3 = 8/27 so, r = 2/3 Now you can find the 1st term and thus whatever terms you want.
*November 24, 2015*

**Algebra**

Been there, done that. http://www.jiskha.com/display.cgi?id=1448344846
*November 24, 2015*

**Math**

well, what is 3 cows plus 6 cows? 3 doughnuts plus 3 doughnuts? whatever x is, you have 3+3 of it.
*November 24, 2015*

**math**

c(x) = 3 + x/3000 + e^(-.003x) c'(x) = 1/3000 - .003e^(-.003x) So, you can see that the cost to produce a unit consists of a fixed amount, plus a steadily decreasing variable amount as more are produced. That means that the cost of the 100th unit is c'(100) = 1/3000...
*November 24, 2015*

**Algebra 1**

without knowing step 4, it's hard to say. Both distributive and associative properties are expressed. I doubt very much that it is a fact, as it's just an expression, with no assertion that it is true.
*November 24, 2015*

**Math,Mensuration**

just plug in your numbers: S = 2πr(r+h) V = πr^2 h
*November 24, 2015*

**math**

If the length is x, then the width is x-4. So, the perimeter is 2(x + x-4) = 56
*November 24, 2015*

**college algebra**

Assuming you meant a bicycle tire makes 3 complete revolutions for each revolution of the pedal then we have (in inches/minute) 100 * 3 * 27π Now just convert that to miles/hour.
*November 24, 2015*

**math**

base = s/2 leg = 2s s/2 + 2*2s + 4s = 34 Now solve for s, and then the triangle's sides.
*November 24, 2015*

**Algebra**

since time = distance/speed, 20/(x-3) + 20/(x+3) = 5
*November 24, 2015*

**Algebra**

just solve t^2-2t = 48 t^2-2t-48 = 0 (t-8)(t+6) = 0 I expect you can take it from there, no?
*November 24, 2015*

**Math**

multiply by -3
*November 24, 2015*

**math**

review the definition of cot(x). You will see that if the height is h, h*cot27° - h*cot29° = 1000
*November 24, 2015*

**Maths**

x+y = 32 4x-5 = 8y Solve for x and y, then x-y
*November 24, 2015*

**Algebra**

If x at 5%, y at 10%, then 200+x+y at 15% x+y+200+x+y = 7000 .05x + .10y + .15(200+x+y) = 815 Now just solve for x and y, and then x+y+200
*November 24, 2015*

**math (check answers)**

looks good to me. nice work.
*November 24, 2015*

**math**

so, do you mean ln(xy-sqrt(x^2-y^2)) or ln(xy)-sqrt(x^2-y^2) I will assume the first, since the 2nd is much easier ∂z/∂x = 1/ln(xy-√(x^2-y^2)) * (y-x/√(x^2-y^2)) and similarly for y.
*November 23, 2015*

**math**

you can use the techniques discussed here http://math.stackexchange.com/questions/783469/evaluate-the-limit-with-taylor-series to break it into pieces, and use the Taylor series to evaluate using the linearity of limits. Each function involved has a relatively easy-to-get series.
*November 23, 2015*

**Physics**

(30 m/s)/(5s) = 30/5 = 6 m/s^2
*November 23, 2015*

**Physics**

(25-15) m/s ------------------ = 2 s 5 m/s^2
*November 23, 2015*

**TECH MATH**

the volume of a cylindrical hole in a sphere is discussed here: http://mathworld.wolfram.com/SphericalRing.html Just plug in your numbers.
*November 23, 2015*

**math**

since 9=3^2, log_3(9^12) = log_3(3^24) = 24 Not quite sure what 9logexponent 12 means.
*November 23, 2015*

**MATH**

6. 60/45 = 4/3 = 12/9 7. (a) 200cents/64floz = 3.125 cents/floz You can do (b) the same way and then compare for (c) 8. 3/10 in = 7/8 mi (3/10)(8/7)in = 1 mi
*November 23, 2015*

**math**

since a sample of 20 contained 13, a bag of 5*20 should contain 5*13
*November 23, 2015*

**calculus**

assuming the usual sloppiness, we have y=(5x^2-45)/(x^2-25) y'= -160x/(x^2-25)^2 y" = 160(3x^2+25)/(x^2-25)^3 since y" is never zero, there are no inflection points, as can be confirmed here: http://www.wolframalpha.com/input/?i=%285x^2-45%29%2F%28x^2-25%29
*November 23, 2015*

**Math**

I guess you are. It is on the line between QII and QIII.
*November 23, 2015*

**Math**

If the lowest and highest are x and y, then we have, adding up all the points: x+5*78+y = 80*7 x+y = 560-390 = 170 (x+y)/2 = 85
*November 23, 2015*

**math**

If he sold x shares, then he'd have made .0214x By selling them, he received 77x Investing them, he bought 77x/100 shares of 6% shares. 77x/100 * .06 = .0462x So, he increased his income by (.0462-.0214)x = 117 x = Rs 4717.74 If the slow pipe takes x minutes, then we have ...
*November 23, 2015*

**Calculus - typo**

or, (-1/r) e^[(-1/r) t] since d/dt e^(kt) = ke^(kt)
*November 23, 2015*

**College Alg.**

If the amounts in A and B are x and y, then (suppressing all the extra zeros), maximize p=.13x+.07y subject to x >= 65/2 y >= 65/4 x+y <= 65 Now use your favorite tool to solve. A good one is at http://www.zweigmedia.com/RealWorld/LPGrapher/lpg.html
*November 23, 2015*