Thursday

July 24, 2014

July 24, 2014

Total # Posts: 23,938

**intro to computer**

B - nothing is free

**Math please help!!**

just plug and chug, using the quotient rule (2^x ln2 - e^x)(2^x+e^x) - (2^x-e^x)(2^x ln2 + e^x) --------------------------------------------------------------- (2^x+e^x)^2 You can simplify that to 2^(x+1) e^x (ln2 - 1) / (2^x+e^x)^2

**math**

90ft * 7ft * (1/2 oz/ft^2) = 90*7*(1/2) oz Note how the ft^2 cancel out, just leaving oz in the result. Watch the units, and they will help you decide how to multiply or divide the ratios.

**Geometry**

The sides are a b=a+12 c=b+24 d=c+36 So, a+b+c+d = 136 a+b+c+c+36 = 136 a+b+2c = 100 a+b+2(b+24) = 100 a+b+2b+48 = 100 a+3b = 52 a+3(a+12) = 52 4a+36 = 52 4a = 16 a = 4 So, the sides are 4,16,40,76

**Math**

if the dept head makes x, then x + 3x = 290000 4x = 290000 x = 72500

**Algebra**

learn to recognize common Pythagorean triples in right triangles. The simplest is 3-4-5. This is just double that, or 6-8-10. The rope is 10 feet long. Or, you can do the algebra, using r^2 = 6^2+8^2 and solve for r.

**hindi**

सर्वाधिक लोकप्रिय में से एक था बकवास कविता का ल&#...

**Math**

C = 2πr, so r = C/2π A = πr^2 = π(C/2π)^2 = C^2/4π In this case, A = 16^2/12 = 21.3

**hct**

evidently the volume of iron is 26.44-25.40 = 1.04 mL. So, the density is 8.2g/1.04mL = 7.88 g/mL

**Algebra**

D/B = 27/16 for all strings. So, For the longer string, D/64 = 27/16 Now just solve for D

**Math help!**

f = secx^cotx log f = cotx * log secx 1/f f' = (-csc^2 x * log secx) + (cotx * secx*tanx/secx) f' = secx^cotx (1 - csc^2(x) log secx)

**trig**

While this might appear to be an exercise in half-angle or double-angle formulas, it is really just a check to see whether you remember your basic trig definitions: cscθ = 1/sinθ and secθ = 1/cosθ You happen to be using θ/2, but the principle holds. so...

**Math**

You were right as far as you went. But, you didn't use the rest of the information they gave you. a+b+c = 22 But what else do we know? If a is the short side (assuming it is indeed an odd integer), then b=a+2 (next odd integer) c=2a (twice as big) So, substituting in the g...

**Algebra/I hope this is the last time.**

why all the embedded words and weird unbalanced parentheses? Just list the points: (0,4) (1,5) (2,6) How ever did you get (2,1)? (-10,-6) (-5,-1) (-4,0) and many more

**Math**

You know that cosθ = x/r In QII, x < 0 and y > 0, so we know x = -2 r = 3 so, y = √5 Now you know that sinθ = √5/3 and you now can easily figure sinθ * tanθ

**math (cant figure it out)**

correct: C(7,2) = 7*6 / 2 = 21

**Algebra**

We already went through f(3/2) and f(b) with f(x) = x^2+2. I answered early this morning, and you said thank you 4 hours ago. Why are you asking for those again? You got f(3/2) correct then. Why are you now not sure? At any rate, just substitute in the value wherever x appears...

**Math (check answer plz)**

I assume you mean 9C4 9C4! = 0 Anyway, 9C4 = 9!/(5!4!) = 9*8*7*6 / 4*2*3*1 = 126 9P4 = 9!/5! = 9*8*7*6 = 3024

**statistics**

since 84+16=100, it appears that 84 have taken politics 16 have taken history 0 have taken both 100 have taken at least one of the subjects.

**algebra/Steve or Damon help**

f(3/2) = (3/2)^2 + 2 = 9/4 + 2 = 4.25 f(b) = b^2+2 how did you get zero?

**math**

r^3 = 3375 r = 15 Now just use S4 = 32.5 to find the cheapest price. I suspect a typo, since $32.5 is such a small number.

**math**

after each step, there is 0.9 as much alcohol as before. So, after 7 steps, the amount of alcohol is 10*0.9^7 = 4.78 liters.

**Math**

x+y=30 25x+30y=810

**Algebra II**

correct

**math**

S3 = 1(1-r^3)/(1-r) = 157 1+r+r^2 = 157 r^2+r-156 = 0 (r-12)(r+13) = 0 r = 12 or -13 So, the GPs are 1,12,144,... 1,-13,169,...

**high school algrebra 1**

for p people, the cost c is c = 25 + 18p the cost per person is 25/p + 18

**math (cant figure it out)**

a cube has 6 faces, so the theoretical probability is 1/6, not 1/30! (B) Why would you divide 120 by the number of spots that show? Would P(5) be 1/24?

**math**

h/75 = tan 62

**Algebra 1**

#1 ok #3 .701 = 0.7 to the nearest tenth. Your rounding doesn't have any tenths!

**Algebra 1**

#1 you cannot divide by zero. So, when the denominator is zero, that value of x must be excluded. So, what is x when 3x-6=0? #2 ok #3 use the quadratic formula for this one. #4 Nope. 4^0 = 1 2^-3 = 1/2^3 = 1/8 So, 1 - 1/8 = 7/8 You calculated 4^0 - 2^3 #5 correct. So why did y...

**algebra 2**

Starting from February, after m months, he has 40m dollars. So, when does 40m = 320? m=8 So, what's 8 months after February?

**Math**

20 cows 70 animals so, 20/70

**Math - incomplete**

Reiny went through this for you once. Now, maybe if you say which side of STU is b, we can make some headway.

**Algebra 1**

You did not factor correctly. x^2-4x+4 = (x-2)(x-2) If that's what you got, then you clearly don't understand what it means. x-2 = 0 when x=2, not -2.

**averages**

8(x+2) = 8x-24+y 8x+16 = 8x-24+y 40 = y It doesn't matter what the average age is. Replacing a 24-year-old by a 40-year-old adds 16 years to the total ages, raising the average by 2.

**physics**

72t + 1/2 at^2 = 70 72 + at = 54 so, a = -16.2 m/s^2 applied for t=10/9 seconds

**maths**

42

**algebra**

since g(3) = 2, g^-1(2) = 3 since h(-4) = 1, h^-1(1) = -4 (h*h^-1)(-7) = h(7)*h^-1(-7) = (-5)*(-8) = 40 If you meant (h◦h^-1)(-7) then that would be -7, since by definition (h◦h^-1)(x) = x.

**Math**

y = 2cos(3x+135) cos(kx) has period 2pi/k, so y has period 2pi/3. The 135 is just a phase shift, and does not affect the period.

**check answer**

correct.

**Geometry**

since area grows as r^2, the area grows by (1/2)^2 = 1/4

**Goemetry**

PQ has length √(2^2+15^2) = √229 P'Q' has length 4 times that.

**math (check answer plz)**

Repeating an experiment naturally gives rise to experimental probability. Since no experiment is described, the probability must be theoretical only. So, (C).

**math**

the clue is that (x+3) divides the volume. So, a little checking shows that the volume v = (x+3)(x-7)(x+9) so, if x+3=15, x=12 and the box is 15x5x21

**math**

surely you have the formula for the period of a pendulum of length L (and small amplitude): T = 2π √(L/g) Now just plug in your numbers.

**Math**

-.05t + 300 = 182 Now just solve for t.

**Calculus**

we just did one of these x(t) = 3t^2 - 18t + c Now just figure x(6)-x(0)

**Maths**

The max occurs when x = -b/2a = 5/4, and is indeed 65/8 wolframalpha.com confirms this: http://www.wolframalpha.com/input/?i=-2x^2%2B5x%2B5

**Maths**

done earlier, and you were correct.

**Algebra**

m = miles g = gallons m = 20g

**math *check***

6 possible outcomes only 1 is a 5 So, theoretical P(5) = 1/6 You rolled 12 times, so that's B: experimentation. Evidently the die was heavily loaded.

**Math**

Correct. Reiny missed the -2x^2. Even experts trip over the details sometimes.

**Calculus**

Oops. Flipped a minus sign f(3) = 9-27+c = -18+c total change is thus -18

**Algebra**

just solve for x in 2771x/(100-x) = 36000 x = 92.85%

**Math**

Let the distance be d. If the kite is between the girls, d/sin75° = 20/sin40° But, if Kate is between the kite and Abigail, then d/sin25° = 20/sin40°

**equation**

after m months, you have 10*3^(m/2)

**Algebra**

0 < L <= 90 2L = 330-2W L = 115-W 0 < 115-W <= 90 90 >= W-115 > 0 205 >= W > 115

**Algebra**

(f-h)(4) = f(4)-h(4) = (2*4+5) - (7-4/3) = ?

**math foundations 20**

you want x such that P(Z<x) = 0.025 That means that x must be more than 1.96 std below the mean. In this case, that's 3.128 years.

**math**

C(12,2)*2 assuming the scoops must be different flavors. If duplicate scoops are allowed, then it's just 12^2 * 2

**Math**

You'll be covering rational functions, asymptotes, logarithms, inverse functions, and more. Go to your local used-book store, and buy a cheap text for Algebra II. Then, go for it -- with more tools at your disposal, the kinds of problems you can solve get much more interes...

**Math 11**

If the marker is at distance x away from the spot just below the balloon, we have h/x = tan 27.8 (h+345)/x = tan 46.2 Eliminate x to get h/tan 27.8 = (h+345)/tan 46.2 Now just solve for h.

**math help plz2!!!!**

from the vertex, we know that y = a(x+3)^2+5 Now plug in the values to get a: 1 = a(-6+3)^2 + 5 9a = -4 a = -4/9 y = -4/9 (x+3)^2 + 5 See http://www.wolframalpha.com/input/?i=y+%3D+-4%2F9+%28x%2B3%29^2+%2B+5

**algebra**

we breathlessly await further developments.

**math**

as with all parabolas, the vertex (in this case a maximum) is at p = -b/2a = 150/.006

**Math**

as with all parabolas, the vertex (in this case a maximum) is at x = -b/2a = 80/0.0002

**MATH**

the length is 270-x So, the area is length*width, or f(x) = x(270-x) As with all parabolas, the vertex is midway between the roots, so in this case, it's at x=135. Since the graph opens downward, the vertex represents the maximum possible area.

**MATH**

from the values of the roots, we know that the functions will be of the form y = ax(x+4) So, pick a positive to open upward, and a negative to open downward. Any nonzero value will do.

**Calculus**

hit the ground == drop 400 ft. So, 16t^2 = 400 Now just solve for t.

**math**

7 filled 8 unfilled Choose 6 of each. So, C(7,6) * C(8,6) = ?

**Math**

If two weigh 51, that's the minimum for two boys, leaving the maximum for the 3rd boy of 3*159-2*51 = 159-102 = 57

**Calculus**

dv/dt = 0.6t cos(0.08t^2-1) v = 3/8 sin(0.08t^2-1) + c Since v(0) = 14, c = 14+3/8 sin(1) = 14.3 v(t) = .375 sin(.08t^2-1)+14.3 Now just evaluate v(10)

**Algebra/could show me how to work this problem**

I suspect a typo. Why not just say 2x^2+1? At any rate, assuming things are correct as written, for any input, just substitute it for all the x's and evaluate for the output. input: -2, output (-2)^2+(-2)^2+1 = 4+4+1 = 9

**Physics-can someone please check this**

(b) The horizontal speed is unaffected by gravity, so it remains 24.5 m/s. In 3 seconds, John travels 3*24.5 = 73.5 meters. (a) we know that the vertical position, starting at y0 is y(t) = y0 - 4.9t^2 Since y(3)=0, we can get the initial height by solving y0 - 4.9*9 = 0 y0 = 4...

**Math**

wow. cubics are not generally easy to solve. Best bet is a graphical or numerical solution. wolframalpha gives http://www.wolframalpha.com/input/?i=4x^3-6.68E-7x^2%2B1.67E-8x-1.04E-10 The root is very close to zero, since the function is very nearly 4x^3=0 Blowing up the graph...

**math**

lose all the nonsense text. You have (x-1)^2 + (x-2)^2 + (x-3)^2 = 0 Now, you know that (x-1)^2 is a parabola, which is tangent to the x-axis at x=1, because of the double root. Similarly, the other two terms are never negative. So, since we are adding up three positive values...

**math**

you start out talking about two numbers, toss in some unknown quotient (maybe not even in lowest terms) then ask for "number"? The question is mighty unclear to me.

**Math**

just add .145258x to both sides and you have 1.145258x = .145258 now divide by 1.145258 and you get x = 0.126834

**Doppler Effect**

for non-relativistic speeds, we can use the approximation. c/520 = (1+v/c) * c/590 520(1+v/c) = 590 1+v/c = 59/52 v/c = 7/52 v = 7/52 c Is that relativistic? Generally, less than 0.1c is considered non-relativistic, so we may be a bit off, but if that matters, use the exact fo...

**mathematics**

The only possible choice assumes a typo where you meant to say that one quarter of x is 36. Then, x is 144. Hmm. Unless the question reads 4 quarters of x is 36. What is 1 quarter of x? Then the answer is 9.

**science**

Assuming you meant 0.400g/dm^3, that translates to 0.0004 g/cm^3 So, 500cm^3 of that means 0.2 g Or, in one step, that's 500 cm^3 * (1dm/10cm)^3 * 0.4 g/dm^3

**physics**

The orbital period is given by T = 2π√(r^3/GM) We want M, which is thus M = r^3/G * (2π/T)^2 Now just plug in your numbers.

**Maths**

Looks to me like they could all be 8. Are there any restrictions on the values allowed? 2014 is not a multiple of 5, so there is no cycle of 5 numbers which repeats.

**Algebra/not sure what to do**

f(x) = x-8 for whatever value x has. So, if x=p, f(p) = p-8 Just replace x with the desired value throughout the entire line.

**math**

I'd say yes. That's what Accounts Receivable are for -- waiting for cash flow to be realized. That's assuming the invoice is not generated until a purchase is confirmed. But, what do I know? I may be off base here.

**Number Theory**

Since the n numbers are divided up in pairs, I'd say n/2 copies. Hence the formula for the sum: n(n+1)/2 Technically, that's [n+1]/2 where [] is the greatest-integer function.

**maths**

If P is x meters from the base of the pole of height h, then h/x = tan 53° h/(x+20) = tan 28° eliminate x and you have h cot 53° = h cot 28° - 20 h = 20/(cot28°-cot53°)

**math**

10(q+7) + 25q = 280

**Maths**

If there are x children, then .6x = 18 x = 30 78? 1? You just throwing darts at numbers? If not, show you r work, so we can help you get it right.

**math**

If we add up terms n through n+10, then we get (n+10)/2 (2a + (n+9)45) - (n-1)/2 (2a+(n-2)45) = 891 11a+495n = -1089 a+45n = -99 If we are adding up the first 11 terms, then a = -144 and T28 = -144+27*45 = 1071 T45 = -144+44*45 = 1836 But, if we add up terms T5 through T15, th...

**Calculus**

Looks good to me.

**Calculus**

x(t) = -cos t + c now you know that x(0) = 3, so plug in t=0 to find c. Then you can use t=2 to get x(2)

**Maths!**

300 = 100 + 40*5 So, set things up as an arithmetic sequence, and find that S41 = 41/2 (100+300) = 8200

**maths**

simple: 10000(1+.12*5) compound: 10000(1+.10)^5 evaluate and compare.

**calculus**

c(x) = 350 + .20 x

**Algebra**

are there any pairs with the same 1st element? If not, it is a function.

**math**

or, using de Moivre's rule, 1+i = √2 cis π/4 so √(1+i) = ∜2 cis π/8 1-i = √2 cis -π/4 so √(1-i) = ∜2 cis -π/8 √(1+i)/√(1-i) = cis π/4 Now the angle doesn't matter, since cos^2+sin^2 = 1

**math**

√(1+i)/√(1-i) = √(1+i)√(1-i) / (1-i) = √(1-i^2) / (1-i) = √2/(1-i) = √2(1+i) / (1-i)(1+i) = √2(1+i)/2 = 1/√2 + 1/√2 i a = 1/√2 b = 1/√2 a^2+b^2 = 1/2 + 1/2 = 1

**Math**

since the slopes are the same, the lines are parallel. Or, in this case, they are the exact same line.

**Math**

Or, knowing that the general circle is (x-h)^2 + (y-k)^2 = r^2 plug in your points to get (-5-h)^2 + k^2 = r^2 h^2 + (4-k)^2 = r^2 (2-h)^2 + (4-k)^2 = r^2 h = 1 k = -19/8 r^2 = 2665/64 and we have the circle as derived above The brute-force way, of course, is to plug your poin...

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