Thursday

August 28, 2014

August 28, 2014

Total # Posts: 24,457

**Math**

you can easily see that K = 18-C So, put that into the 2nd equation and you have 2(18-C)+4C = 50 36-2C+4C = 50 2C = 14 C = 7 So, K = 11
*June 14, 2014*

**math**

x^3+3x = x(x^2+3) = (a^2/3-a^-2/3)((a^2/3-a^-2/3)^2+3) = (a^2/3-a^-2/3)(a^4/3 + 1 + a^-4/3) Note we have the factorization of the difference of two cubes: = a^2 - a^-2
*June 14, 2014*

**Another this math tho**

ding ding -- we have a winner!
*June 13, 2014*

**this math tho**

well, does 3(-10)+54 = 18?
*June 13, 2014*

**3 questions Math**

Oops. The synthetic division site was http://www.mathportal.org/calculators/polynomials-solvers/synthetic-division-calculator.php
*June 13, 2014*

**3 questions Math**

#18 - did you try this at the syntehtic division site I gave you? You can see polynomial long division at calc101.com; click on the "long division" button. #19 If you meant 1/(2x + 14) - 9/(x + 7) = -6 then that's just 1/(2x+14) - 18/(2x+14) = -6 -17/(2x+14) = -6...
*June 13, 2014*

**Algebra ll**

take a visit to http://www.mathportal.org/calculators/polynomials-solvers/synthetic-division-calculator.php and enter your coefficients. It will show the calculation, and even explain it if needed. It's hard to do it here, due to browser formatting of html.
*June 13, 2014*

**Algebra**

just find when the two are equal: 16x+150 = -x^2+60x-10 x^2 - 44x + 160 = 0 (x-40)(x-4) = 0 Now the answer should be clear.
*June 13, 2014*

**algerbra**

try something like this: http://www.wolframalpha.com/input/?i=3x%2By+%3C%3D+5 you can type in many different things, and it will show you the solution
*June 13, 2014*

**algebra 2**

B(t) rose by 32
*June 13, 2014*

**Algebra (Factoring)**

2(x^4-5x^2-36) 2(x^2+4)(x^2-9) 2(x^2+4)(x-3)(x+3)
*June 13, 2014*

**Algebra**

x/5 = 40/1.6 x/150 = 1.6/40 solve for x
*June 13, 2014*

**Math**

99 action means 55 horror, for a total of 154 films in 7 days. That's 22 films/day on average.
*June 13, 2014*

**geometry**

Assuming the sun rises at 6 am and sets at 6 pm, then at 9 am it is 45° above the horizon. That means a 147cm person will cast a 147cm shadow.
*June 13, 2014*

**science**

total mass of H2SO4 is 98 So, figure the % mass of each of the elements: H2 = 2 S = 32 O4 = 64
*June 13, 2014*

**Math**

since √x is not real for x < 0, we need 5y+1 >= 0 y >= -1/5 3y-5 >= 0 y >= 5/3 So, we need y >= 5/3 for the domain Now proceed to solve: √(5y+1) - √(3y-5) = 2 5y+1 - 2√[(5y+1)(3y-5)] + 3y-5 = 4 8y - 8 = 2√[(5y+1)(3y-5)] (4y-4)^2...
*June 12, 2014*

**maths**

This is just a work problem in disguise. Together the cars must cover a distance. 1/x = 1/4 + 1/6 = 5/12 x = 12/5 Check. Say the distance is 120 miles In 2.4 hours, the car covers 2.4/4 = 0.6 the distance. In 2.4 hours, the van covers 2.4/6 = .4 the distance. ok
*June 12, 2014*

**math**

you can order n things in n! ways. 24! = 6.2 * 10^23
*June 12, 2014*

**Math**

v = pi r^2 h So, just plug in r=3.7m and h = 2.4m
*June 12, 2014*

**MATH**

as you know, the derivative of e^u = e^u u' So, ∫e^u du = e^u Here, u = -x, so du = -dx You thus have ∫e^u (-du) = -∫e^u du = -e^u = -e^-x
*June 12, 2014*

**Algebra**

no way to tell
*June 12, 2014*

**Algebra**

If the first takes x hours, 1/x + 1/(x+5) + 1/(3x) = 1/(9/4) x = 4 So, the 3 pipes require 4,9,12 hours.
*June 12, 2014*

**Arithmetic**

1/3 of the marbles are green. So, 1/3 of at least 54 are green. How many is that?
*June 12, 2014*

**whole number**

1219 - 32 - 24 = ?
*June 12, 2014*

**Science(electric circuits)**

hmmm. The current in each parallel path may be different. That's a pretty open question, with no context.
*June 12, 2014*

**englewood**

total income,state,city tax is 6% 6% of 215 = 12.90 So, total deductions are 15.16+29.33+12.90 = 57.39 Net income is thus 215.00-57.39 = $157.61 Who says we are not taxed enough?
*June 12, 2014*

**science-chemistry**

.00565*450 = 2.54g of NaCl So, how many moles is that?
*June 12, 2014*

**Math**

I'm having a little trouble visualizing the angles in question. If we label the boats A and B and the dock D, which angles are we talking about?
*June 12, 2014*

**Intro to Algebra**

the area of a trapezoid is (b+B)h/2. Since we have 4 trapezoids with bases 5 and 6, the total area is 4(5+6)h/2 = 22h ft^2 paint costs $10/33ft^2 = .3030 $/ft^2 cost of $40 means 132 ft^2 22h = 132, so h=6 ft
*June 12, 2014*

**Math**

8^m 3^m = 24^m 576 = 24^2, so 24^(2(m-4)) = 24^m 2(m-4) = m 2m-8 = m m = 8
*June 12, 2014*

**math - ouch**

Good catch, Reiny - I was a bit sloppy.
*June 12, 2014*

**math**

cos3x = cos2x we need 3(x+2m*pi) = 2(x+2n*pi) for some m and n. Some playing around will get you x = 0,2/5 pi, 4/5 pi or, in degrees, x = 0,144,288
*June 12, 2014*

**math**

Facts as presented: g+p+c = 100 21g+8p+3c=600 since c = 100-(g+p), 21g+8p+3(100-g-p) = 600 21g+8p+300-3g-3p = 600 18g+5p = 300 Since 5p = 300-18g, g must be a multiple of 5. But, since g is even, it must be 10,20,30,... If g=10, p=24 If g=20, 18g=360, so any number g>10 ...
*June 12, 2014*

**intro to computer**

B - nothing is free
*June 12, 2014*

**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
*June 11, 2014*

**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.
*June 11, 2014*

**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
*June 11, 2014*

**Math**

if the dept head makes x, then x + 3x = 290000 4x = 290000 x = 72500
*June 11, 2014*

**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.
*June 11, 2014*

**hindi**

सर्वाधिक लोकप्रिय में से एक था बकवास कविता का ल&#...
*June 11, 2014*

**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
*June 11, 2014*

**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
*June 11, 2014*

**Algebra**

D/B = 27/16 for all strings. So, For the longer string, D/64 = 27/16 Now just solve for D
*June 11, 2014*

**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)
*June 11, 2014*

**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...
*June 11, 2014*

**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 ...
*June 11, 2014*

**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
*June 11, 2014*

**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
*June 11, 2014*

**math (cant figure it out)**

correct: C(7,2) = 7*6 / 2 = 21
*June 11, 2014*

**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...
*June 11, 2014*

**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
*June 11, 2014*

**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.
*June 11, 2014*

**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?
*June 11, 2014*

**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.
*June 10, 2014*

**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.
*June 10, 2014*

**Math**

x+y=30 25x+30y=810
*June 10, 2014*

**Algebra II**

correct
*June 10, 2014*

**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,...
*June 10, 2014*

**high school algrebra 1**

for p people, the cost c is c = 25 + 18p the cost per person is 25/p + 18
*June 10, 2014*

**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?
*June 10, 2014*

**math**

h/75 = tan 62
*June 10, 2014*

**Algebra 1**

#1 ok #3 .701 = 0.7 to the nearest tenth. Your rounding doesn't have any tenths!
*June 10, 2014*

**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 ...
*June 10, 2014*

**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?
*June 10, 2014*

**Math**

20 cows 70 animals so, 20/70
*June 10, 2014*

**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.
*June 10, 2014*

**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.
*June 10, 2014*

**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.
*June 10, 2014*

**physics**

72t + 1/2 at^2 = 70 72 + at = 54 so, a = -16.2 m/s^2 applied for t=10/9 seconds
*June 10, 2014*

**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.
*June 10, 2014*

**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.
*June 10, 2014*

**check answer**

correct.
*June 9, 2014*

**Geometry**

since area grows as r^2, the area grows by (1/2)^2 = 1/4
*June 9, 2014*

**Goemetry**

PQ has length √(2^2+15^2) = √229 P'Q' has length 4 times that.
*June 9, 2014*

**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).
*June 9, 2014*

**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
*June 9, 2014*

**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.
*June 9, 2014*

**Math**

-.05t + 300 = 182 Now just solve for t.
*June 9, 2014*

**Calculus**

we just did one of these x(t) = 3t^2 - 18t + c Now just figure x(6)-x(0)
*June 9, 2014*

**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
*June 9, 2014*

**Maths**

done earlier, and you were correct.
*June 9, 2014*

**Algebra**

m = miles g = gallons m = 20g
*June 9, 2014*

**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.
*June 9, 2014*

**Math**

Correct. Reiny missed the -2x^2. Even experts trip over the details sometimes.
*June 9, 2014*

**Calculus**

Oops. Flipped a minus sign f(3) = 9-27+c = -18+c total change is thus -18
*June 9, 2014*

**Algebra**

just solve for x in 2771x/(100-x) = 36000 x = 92.85%
*June 9, 2014*

**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°
*June 9, 2014*

**equation**

after m months, you have 10*3^(m/2)
*June 9, 2014*

**Algebra**

0 < L <= 90 2L = 330-2W L = 115-W 0 < 115-W <= 90 90 >= W-115 > 0 205 >= W > 115
*June 9, 2014*

**Algebra**

(f-h)(4) = f(4)-h(4) = (2*4+5) - (7-4/3) = ?
*June 9, 2014*

**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.
*June 9, 2014*

**math**

C(12,2)*2 assuming the scoops must be different flavors. If duplicate scoops are allowed, then it's just 12^2 * 2
*June 9, 2014*

**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 ...
*June 8, 2014*

**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.
*June 8, 2014*

**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
*June 8, 2014*

**algebra**

we breathlessly await further developments.
*June 8, 2014*

**math**

as with all parabolas, the vertex (in this case a maximum) is at p = -b/2a = 150/.006
*June 8, 2014*

**Math**

as with all parabolas, the vertex (in this case a maximum) is at x = -b/2a = 80/0.0002
*June 8, 2014*

**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.
*June 8, 2014*

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