Thursday

November 27, 2014

November 27, 2014

Total # Posts: 27,026

**Math**

well, r = -3/6 = (3/2)/-3 = (-3/4)/(3/2) ... 6/2 = ? (-1/2)/1 = ?
*October 8, 2014*

**Math**

have you a calculator? Just do the math...
*October 8, 2014*

**Sociology (Stats) Std. Dev**

600 is 1 std above the mean. 300 is 3 std below the mean. Just look up the tails in your table. Or, play around some at http://davidmlane.com/hyperstat/z_table.html
*October 8, 2014*

**help**

h(t) = 5 + 70t - 16t^2
*October 8, 2014*

**math**

5% up, or 5% down? In any case, what's 5% of 85000?
*October 8, 2014*

**math**

It's roughly 55000/50 = 1100 the estimate will be low, because we lowered the divided and raised the divisor.
*October 7, 2014*

**Math**

#1 clearly, r = -1/2 T11 = ar^10 #2 a(-2)^9 = -1024 #3 Just recall that S = a/(1-r) then plug in the numbers
*October 7, 2014*

**pre-calculus**

well, 9 is half of 18, so ...
*October 7, 2014*

**Math**

#1 think 8^n #2 .123 123 123 = 123/999 same for the others
*October 7, 2014*

**calculus**

The math looks good to me, but the negative answer is strange because the question was, how fast is the angle increasing? That is because dx/dt = -600; the plane is approaching the kangaroo. Hailey, did you do as Reiny asked, and check his math?
*October 7, 2014*

**math**

20 kg * 2.2 lb/kg * 50 mg/lb * 1mL/100mg = 22 mL
*October 7, 2014*

**Math**

well, what's the mean? 86.2 The deviations from the mean are thus 8.2, 4.2, ... Now just take the mean of those values. That's the mean deviation.
*October 7, 2014*

**Pre-Calc/Trig..**

I think I prefer y = 2(x-3)^2
*October 7, 2014*

**Calculus question**

simple, but tedious. See http://en.wikibooks.org/wiki/Trigonometry/Simplifying_a_sin%28x%29_%2B_b_cos%28x%29
*October 7, 2014*

**math/physics**

conserve momentum: 0.600(+4.00) + 1.00(-5.00) = 1.00(-7.25) + 0.600v v = +7.75 Now, what's wrong with this picture?
*October 7, 2014*

**Calculus**

of course -- where y=0
*October 7, 2014*

**Algebra**

I get 2.9 how did you get your answer?
*October 7, 2014*

**math**

if the angle is x, 12/22 = tan(x)
*October 7, 2014*

**Math**

apparently the formula is d = v√(h/4.9) multiply that by √4.9/√4.9 and you have d = v√(4.9h)/4.9 Now just plug in the numbers.
*October 7, 2014*

**physics**

PE at top: mgh = 35.9*9.8*20.3 = 7142 J She loses half that on the way down. KE = 1/2 mv^2 = 3571 So, v^2 = 3571/35.9 = 99.47 Call it 100 So, v = 10
*October 7, 2014*

**calculus**

√(2x+4y) + √(2xy) = 13.4 (x+2y) / 2√(2x+4y) * (2+4y') + 1/(2√xy) * (2y + 2xy') = 0 (x+2y)/√(2x+4y) + 2(x+2y)y'/√(2x+4y) + √(y/x) + √(x/y) y' = 0 y' = -[(x+2y)/√(2x+4y)+√(y/x)]/[2/√(2x+4y...
*October 7, 2014*

**Calculus**

The distance traveled after t hours is: If boat N is at (0,y) boat E is at (x,0), then the distance z from N to E is z^2 = x^2+y^2 At the given moment, z=√(56^2+20^2) = √3536 = 4√221 2z dz/dt = 2x dx/dt + 2y dy/dt Now plug in the numbers (after canceling out ...
*October 7, 2014*

**math**

I'd say 2x where x is the cost of one book
*October 7, 2014*

**AP Calculus**

f(x+h) = 1/√(x+h) + x+h f(x) = 1/√x + x f(x+h)-f(x) = 1/√(x+h) - 1/√x + h = (x+h)^(-1/2) - x^(-1/2) + h From the binomial theorem, (a+b)^n = a^n + n a^n-1 b + ... (x+h)^(-1/2) = x^(-1/2) - 1/2 x^(-3/2)h + 3/8 x^(-5/2)h^2 + ... where ... is stuff with ...
*October 7, 2014*

**Algebra**

Woah! Where did the 15# bags come from? Clearly, there will be more bags if the hold less.
*October 7, 2014*

**math**

ever heard of a calculator? Why would you post such a trivial problem? It takes much less time just to punch it in on your calculator, and you don't have to wait for and endure snide replies. Do you not trust your calculator? Is there something else about multiplication ...
*October 7, 2014*

**Math**

assuming you want trim all around, and plan to use miter cuts at the corners, then you need 2(10 3/4 + 129/10 3/4) = 45 1/2 ft see how much was left unsaid?
*October 7, 2014*

**Grammar**

No ideas on any of them? Nominative case: I,he,she,we,they Objective case: me,him,her,us,them So, #3 she #6 them #7 our -- why? "our" is an adjective can you get the others?
*October 7, 2014*

**math**

if the area is 42 m^2, the side is √42 m So, the perimeter is 4√42 m. Now just do the math...
*October 7, 2014*

**Physics**

no calculus needed. Just plug in your formulas: h(x) = tanθ x - g/(2 (v cosθ)^2) x^2 = 0.75x - .0000547 x^2 That is just a parabola with vertex at (6855.6,2570.8) I expect you can find x when h=0.
*October 6, 2014*

**math**

clearly that would be 6*18 - 4*6 = ?
*October 6, 2014*

**ap calc**

lim (x->3) 4-(√(25-x2))/(3-x) Use l'Hospital's Rule to get = lim (x->3) (x/√(25-x^2)]/(-1) = (3/4)/(-1) = -3/4 Recall that dy/dx at any point on the circle is -x/y
*October 6, 2014*

**Physics**

yes. Friction is just another force; nothing special about it.
*October 6, 2014*

**College Physics**

a = (-284.4 m/s)/1.4s = -203.1 m/s^2 s = Vo t + 1/2 at^2 = 284.4*1.4 - 1/2 (203.1)(1.4^2) = 199.1 m
*October 6, 2014*

**Math**

If each member makes x candles, then 40x = 39(x+3) x = 117 So now you can find the total.
*October 6, 2014*

**MATH**

d/dx (x^5 + y^8) is indeed 5x^4 + 8y^7 y' Usually this is done in conjunction with implicit derivatives, where you have some equation like x^5 + y^8 = 7 and you wind up with y' = -5x^4/8y^7 which you then have to evaluate at some point. ------------------------------ h...
*October 6, 2014*

**AP Calc**

y^2 = x^2 + 4/x 2y y' = 2x - 4/x^2 y' = (2x^3-4)/x^2 * 1/2y = (x^3-2) / x^2y Now as long as y≠0, y'=0 when x=∛2 y(∛2) = ±√(∛4+4/∛2) = ±√(6/∛2) so that's ok. It looks like the only place with ...
*October 6, 2014*

**algebra**

Since F=k∆x, F/∆x is constant. So, if the unstretched length is Lo, 8/(76-Lo) = 14/(85-Lo) Lo = 64 cm
*October 6, 2014*

**Pre Calculus**

What part of your text's explanation don't you understand? Any explanation we can give here will say basically the same thing.
*October 6, 2014*

**Math**

plug in the values graph the function
*October 6, 2014*

**Math**

since y = 10/x, the slope of the tangent at (x,y) is -10/x^2 so the normal has slope x^2/10. So, we have a line with slope y/x = (10/x)/(x^2/10) = 100/x^3 so, where does 10/x = 100/x^3? x = √10 So, at (√10,√10), the slope is 1, and the normal line is just y = x
*October 6, 2014*

**Math**

Man, you're a better grouper than I am. The 18 made me think of 9*2, so I got x(x-3)^2 = x^3-6x^2+9x hmm. too many x^2, so 2(x-3)^2 = 2x^2-12x+18 aha - (x+2)(x-3)^2
*October 6, 2014*

**Algebra**

if a/b = q remainder r, then a = b*q + r Try it with some small numbers: 37/8 = 4R5 4*8+5 = 37
*October 6, 2014*

**Algebra2**

just solve the way you do an equation. Apply a step to all parts of the setup: -1 < 3+2x < 11 subtract 3: -4 < 2x < 8 divide by 2 -2 < x < 4 Ta-da! The other is even easier, since each is separate 1-x > -3 1+3 > x 4 > x 5x-1 > 19 5x > 20 x >...
*October 6, 2014*

**Algebra II**

We have a winner!
*October 6, 2014*

**Algebra II**

4(4x+1)^2 = 4(16x^2+8x+1) Better double-check your answer.
*October 6, 2014*

**Pre Calculus**

No, what it says is (x-c) is a factor of f(x). If (x-c) is a factor of f(x), then f(c) = 0 f(-2) = -4(-8)+5(4)+8 = 32+20+8 ≠ 0 So, (x+2) is not a factor of f(x). You can check this out at calc101.com by clicking on the "long division" button and entering your ...
*October 6, 2014*

**Pre Calculus**

I think you mis-stated the problem. Better go back and see just what the theorem says.
*October 6, 2014*

**math geometry**

As usual, draw a diagram. Half the chord is of length 4. Draw the radius through the chord's center. Now you have a right triangle with leg 4 and hypotenuse 8, which subtends an angle x such that sinx = 1/2 So, x = 30 degrees. The whole chord thus subtends an angle of 60 ...
*October 6, 2014*

**Math**

if f(ax) = af(x), f(x) = kx for some k. check: f(ak) = k(ax) = a(kx) = af(x) f(x+y) = k(x+y) = kx+ky = f(x)+f(y) So, since f(1) = pi, f(x) = pi*x f'(-1) = pi In fact, f'(x) = pi for any x.
*October 6, 2014*

**Math- AP Calc**

3x+xy+4y=8 3 + y + xy' + 4y' = 0 y'(x+4) = -(y+3) y' = -(y+3)/(x+4) y" = -[(y')(x+4)-(y+3)(1)]/(x+4)^2 = -[-(y+3)/(x+4)*(x+4) - (y+3)]/(x+4)^2 = -(-3-y-y-3)/(x+4)^2 = (2y+6)/(x+4)^2 check: 3x+xy+4y=8 y = (8-3x)/(x+4) y' = -20/(x+4)^2 y" = 40/(...
*October 6, 2014*

**Math Proof**

well clearly, since b_n is between 0 and a_n, as a_n->0, so does b_n. Not sure (b) follows. There must be some other conditions on the sequences.
*October 6, 2014*

**word problems**

since time = distance/speed, d/(12-2) = d/(12+2) + 1 d = 35 miles check: 35/10 = 3.5 35/14 = 2.5
*October 6, 2014*

**clemson**

If each pen is x by y, with the x side parallel to the river, then 6x+4y = 1680 a = 3xy = 3*x(1680-6x)/4 = (2520x-9x^2)/2 This is just a parabola with vertex (hence maximum area) at x = 140 So, each pen is 140 by 210 As usual, the fencing is divided equally between lengths and...
*October 6, 2014*

**Math**

not unless i√12 = √12 I think you meant 4±√-12 = 4±i√12 If so, then you are correct
*October 6, 2014*

**Geometry**

Now, if you meant to shift it 3 left and 8 down, then (8,3)+(-3,-8) -> (5,-5)
*October 6, 2014*

**Geometry**

singular is vertex, not vertice. Grr. (8,3) + (x-11,y-11) -> (x-3,y-8)
*October 6, 2014*

**math**

$591.12/72hr = $8.21/hr
*October 6, 2014*

**Algebra**

2x + 6/x = 79/5 10x^2 + 30 = 79x 10x^2 - 79x + 30 = 0 (5x-2)(2x-15) = 0 ...
*October 6, 2014*

**Pre-Calc/Trig...**

y = (x^2-4x+4) - 5+4 = (x-5)(x+1)
*October 6, 2014*

**math**

3(u-2) = 4(u+3) 3u-6 = 4u+12 u = -18 check: -20/-15 = 4/3 yes
*October 6, 2014*

**Math, ASAP Please**

Looks like D to me. Sheesh!
*October 6, 2014*

**Calculus**

depends on where the man is. If the man's distance is x, and the shadow has length s, then (x+s)/15 = s/6 Now just differentiate and plug in the distance when you finally deign to include it.
*October 6, 2014*

**Timerate problem(calculus)**

v = 1/3 pi r^2 (2r) = 2/3 pi r^3 at r=8, dv/dt = 2 pi r^2 dr/dt Now we just have to decide what "at what rate is the increasing" means
*October 6, 2014*

**math**

because 1/5 = 5^-1
*October 6, 2014*

**ALGEBRA**

It will take x days, where 1/x = 1/10 + 1/12
*October 6, 2014*

**Maths**

Apparently the sides are in the ratio b = 3/5 (a+c) c = 1/7 (a+b) a^2 = 144 a,b,c = 12,9,3 so, area = 144+81+9 = 234
*October 6, 2014*

**Maths**

If the bottles cost $x each, then 7x + 13.20 = 10x
*October 6, 2014*

**geometry**

(40-2*2)(20-2*2) = ?
*October 6, 2014*

**Math**

4/7
*October 5, 2014*

**Math**

no way to tell. How tall is the human?
*October 5, 2014*

**Algebra**

well, just plug in the points: a|1-b|+c = 4 a|3-b|+c = 8 a|8-b|+c = 3 a = -2, b = 17/4, c = 21/2
*October 5, 2014*

**Algebra**

a good site for long division is calc101.com Click on the long division button, and you can see all the details.
*October 5, 2014*

**Calculus**

As you can see from the graphs at http://www.wolframalpha.com/input/?i=plot+y%3De^%282x%29%2C+y%3D2x you missed the mark. So, let's see what happened. At the point (x,y) on the curve, the slope is 2e^(2x). A line with slope 2e^(2x) through the origin: e^(2x)/x = 2e^(2x) x...
*October 5, 2014*

**math factoring**

2x^4+12x^3-18x^2-108x 2x(x^3+6x^2-9x-54) Now use grouping 2x(x^2(x+6)-9(x+6)) 2x(x^2-9)(x+6) 2x(x-3)(x+3)(x+6)
*October 5, 2014*

**Math**

g'(x) = f(x^2) + xf'(x^2)(2x) = f(x^2) + 2x^2 f'(x^2) So, at x=2, g'(2) = f(4) + 8f'(4) = 4+8(-3) = -20 g(2) = 2f(4) = 8 So, now we have a point and a slope: L(x) = -20(x-2) + 8 = -20x+48
*October 5, 2014*

**Math**

A = 4pi r^2 dA = 8pi r dr Now plug in the numbers. Recall that % error is dA/A * 100
*October 5, 2014*

**math**

Hint: The only common divisors of 24 and32 are 2,4,8
*October 5, 2014*

**9th grade algebra**

Are you German? What's With All The Capitalization? The lope of the line is (190-120)/2 = 35 y = 50 + 35x
*October 5, 2014*

**Math**

at depth y, the radius of the water surface is r = (10/22)x = 5/12 x So, at depth y, the volume of water is v = 1/3 π (5/12 y)^2 = 25/432 π y^2 dv/dt = 25/216 π y dy/dt 30 = 25/216 π (14) dy/dt 30 = 5.08 dy/dt dy/dt = 5.89 ft/min As always, check my math.
*October 5, 2014*

**statistics**

Seems to me just like drawing from a pack of cards without replacement. p = 136/500 * 135/499 * 134/498 = 0.0198
*October 5, 2014*

**solve long divison polynomials**

A good site for long division is ath calc101.com Just click on the "long division" tab to see all the details, in proper formatting.
*October 5, 2014*

**cobet, maths**

Umm, didn't you just say that 33 like both?
*October 5, 2014*

**calculus**

First off, I suspect a typo. Why have two y^2 terms? I figure you meant x^2 + 4xy +4y^2=40 Just do things term by term, and don't forget the product rule: 2x + 4y + 4xy' + 8yy' = 0 y'(4x+8y) = -(2x+4y) y' = -1/2 Weird, huh? Not if you note that x^2 + 4xy +...
*October 5, 2014*

**math**

Ummm. First off, what do M and O have to do with the length of AB?
*October 5, 2014*

**Math**

4x^2+4y^2-8x-20y+13=0 rearrange things a bit and you get 4x^2-8x + 4y^2-20y = -13 4(x^2-2x) + 4(y^2-5y) = -13 Now complete the squares: 4(x^2-2x+1) + 4(y^2-5y+25/4) = -13 + 4(1) + 4(25/4) 4(x-1)^2 + 4(y - 5/2)^2 = 16 (x-1)^2 + (y - 5/2)^2 = 4 Now does it look familiar?
*October 5, 2014*

**Math**

what's to solve? You have just defined a function.
*October 5, 2014*

**physics**

The situation can be modeled as though the 1st tank were stationary, and the 2nd tank were retreating at 20 m/s. The horizontal and vertical components of the shell's speed at firing are x: 43.4 m/s y: 246.2 m/s So, the height of the shell is h(t) = 246.2t - 4.9t^2 It hits...
*October 5, 2014*

**Algebra**

father's age is f. My age is m. (f-4) = 4(m-4) f+m = 53 Now just solve for f and m.
*October 5, 2014*

**Pre-Calc**

well, it's just f(x)/g(x) = (1/x)/(x^3) = 1/x^4 And I'm sure you can figure the domain. It's where the denominator is not zero.
*October 5, 2014*

**Math**

clearly, it's b and c try dividing out the x^2 factor
*October 5, 2014*

**Calculus**

You have ∫√(u^2-a^2) du, so set u = a secθ du = a secθ tanθ u^2-a^2 = a^2 tan^2θ so it becomes ∫ (a tanθ)(a secθ tanθ) dθ = a^2∫secθ tan^2θ dθ = a^2∫sec^3θ - secθ dθ Now, we all...
*October 5, 2014*

**Calculus**

well, if y = sin^2(u) y' = 2 sinu cosu u' u' = ln3 3^x y' = 2ln3 3^x sin(3^x) cos(3^x) = ln3 3^x sin(2*3^x) I think you got some of your 3's mixed up as powers of sin. You appear to have taken the derivative of sin^3 (3^x)
*October 5, 2014*

**Algebra 2 (Please, help me!)**

Take |x| shrink it horizontally by a factor of 2: |2x| shift it down 3: |2x|-3 Now shrink it vertically by a factor of 4: (|2x|-3)/4 http://www.wolframalpha.com/input/?i=plot+y%3D|x|%2C+y%3D%28|2x|-3%29%2F4
*October 4, 2014*

**Math**

Since the border is on both sides, 5 + 2(2 1/4) = 9.5 7 + 2(2 1/4) = 11.5 2(9.5+11.5) = 42
*October 4, 2014*

**Math**

X^2+4x=10 x^2+4x+4 = 10+4 (x+2)^2 = 14 x+2 = ±√14 x = -2±√14
*October 4, 2014*

**Math**

that will of course be x miles where 100+.60x = 50+.80x
*October 4, 2014*

**algebra**

How could a quadratic be anything like a linear function?
*October 4, 2014*

**algebra**

You could think of it as a shifted parabola, where 2x+3(x-2)^2 = 3(x-2)^2 + 2(x-2) + 4
*October 4, 2014*

**algebra**

Is there a question in there somewhere?
*October 4, 2014*

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