Saturday

October 25, 2014

October 25, 2014

Total # Posts: 26,089

**Algebra**

<mumble>
*October 9, 2014*

**Algebra**

AAAaaarrgh!
*October 9, 2014*

**Algebra 2**

mumble
*October 9, 2014*

**ALGEBRA 2**

First, fix the typos!
*October 9, 2014*

**Algebra**

First, fix the typos!
*October 9, 2014*

**Physics**

well, you know that y(t) = 27t - 4.9t^2 y=0 when 27t-4.9t^2 = 0 t = 27/4.9 = 5.51 You are close, but I wonder how you got what you did... Ah. I see you used g = 10 m/s^2, not 9.8 OK, you are correct.
*October 9, 2014*

**Algebra 2**

#1 Since y = 34-x, x-(34-x) = 20 2x = 54 x = 27 y = 7 #2 There's a typo. If you meant to say -5x+9y = 11, do a little multiplying to get rid of y: -21x+18y = 33 -10x+18y = 22 -11x = 11 x = -1 y = 2/3 If it was -5x+9y = -11, then x = -5 y = -4
*October 9, 2014*

**Algebra 2**

#1 Since x = 3y-4, -3(3y-4)+4y = -3 now just solve for y and then x #2 Since x = 4+4y, -(4+4y) = 4y=-4 or something Again, solve for y, then x
*October 9, 2014*

**Algebra 2**

it would help to know just what it is you are after. All I see is a couple of set definitions.
*October 9, 2014*

**Math**

The relative max/min occur at x = -2,2 as you said. Since f"(-2) < 0, f(x) has a max at x = -2 (f is concave down) Since f"(2) > 0, f(x) has a minimum at x=2 (f is concave up) f(-5) = -65, so the absolute minimum of f(x) on [-5,2] is at x = -5, but that is just...
*October 9, 2014*

**Math (please check)**

It appears to me that you have a product, not a quotient. If f(x) = (t^2 + t^0.5)(t^0.5 - t^-0.5) f'(x) = (2t+0.5t^-0.5)(0.5t^-0.5 + 0.5t^-1.5) = 2.5t^1.5 - 1.5t^0.5 + 1 This can be checked since if we expand f(x), we get f(x) = t^2.5 - t^1.5 + t - 1 f'(1) = 2.5-1.5+1...
*October 9, 2014*

**Calculus**

Since both C and P are monthly amounts, I will assume we are looking for the monthly cost per passenger. That would, of course, be C/P = (100+t^2)/(1000+t^2) As you say, (C/P)' = 1800t/(1000+t^2)^2 So, at t=6, (C/P)' = 0.01006246 Close, but I wonder what happened down ...
*October 9, 2014*

**Math! Please check!**

correct
*October 9, 2014*

**Math! Please check!**

correct Certainly not B: (where the heck is D?)
*October 9, 2014*

**math**

what's 62-43?
*October 9, 2014*

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

correct
*October 9, 2014*

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

that would have to be an even power, with a negative coefficient on the highest power.
*October 9, 2014*

**math-physics**

the problem is, 200kg is the mass, not the weight. You forgot to multiply by g=9.81 You did W = ms, not W=fs If you had kept track of the units, you'd have spotted your error. kg * m ≠ work
*October 9, 2014*

**Math**

law of sines: smallest angle opposite smallest side. That would be between the sides of 24 and 30. The law of cosines tells us that 20^2 = 24^2 + 30^2 - 2(24)(30) cosθ Now just do the math
*October 9, 2014*

**Maths**

reverse the scale. Multiply the lengths by 3:2
*October 9, 2014*

**Math: Differential Equations**

Hmmm. I also believe that the domain is all reals except x=1.
*October 9, 2014*

**math**

y = (4x-8)/(x+1) y' = 12/(x+1)^2 So, y(0) = -8 y'(0) = 12 Now you have a point (0,-8) and a slope (12), so the tangent line is y = 12x-8 See http://www.wolframalpha.com/input/?i=plot+y%3D%284x-8%29%2F%28x%2B1%29%2Cy%3D12x-8+for+x+%3D+-1+to+3
*October 9, 2014*

**Algebra 2**

a+c = 55 25a+20c = 1300 Now just solve for a and c.
*October 9, 2014*

**math**

no way. There are lots of triangles with those two sides. If the 3rd side is x, all you know is that 2.5-1.6 < x < 2.5+1.6
*October 9, 2014*

**Math**

1/2 = 4/8
*October 9, 2014*

**math**

P(chosen) = .75 P(all chosen) is therefore .75^11
*October 9, 2014*

**Math**

range is the difference between the least and the greatest values So, look at the data and do the math.
*October 9, 2014*

**Science Physics**

Well, you have the formula F = GMm/r^2 So, plug in the numbers. What do you get? Oh, OK. The astronaut's mass is thus m = Fr^2/GM
*October 9, 2014*

**Math**

the midpoint is just the average of the two ends. In this case, that is (2500+7000)/2
*October 8, 2014*

**Math! Please check!**

Nope. 90-37 = 53, not 63. I suspect you saw the 9 and the 3 and subtracted to get 6, but nnnoooooo...
*October 8, 2014*

**biology**

google "scientific method" Pick the explanation you find easiest to understand.
*October 8, 2014*

**Geometry**

The equilateral triangle has area 25√3 So, now we have 3 isosceles triangle, each of area 5h, which add up to 25√3. Each concrete triangle thus has area 25/√3, so their height is 5h = 25/√3 h = 5/√3
*October 8, 2014*

**Physics**

We have a parabola, with y(0) = 0 y(2.0) = 0.55 is the vertex That means its equation is y = 0.1375(4-(x-2)^2) The slope at x=0 is 0.55 sin 32° = 0.53 So, the given data are not exact, but probably close enough. So, using 32° as our benchmark, with tan32° = 0.625, ...
*October 8, 2014*

**Physics**

set the staring point at (0,0) Now, figure the relative displacement of each leg of the trip: (200 cos(180-20)°, 200 sin(180-20)°) (300 cos(90+40)°, 300 sin(90+40)°) (400 cos(90-10)°, 400 sin(90-10)°) Now just add up the x- and y-displacements to get ...
*October 8, 2014*

**Algebra**

5.815 = 5 815/1000 6.021 = 6 21/1000 Naturally, the sums are equal. I expect you can reduce the fractions as necessary.
*October 8, 2014*

**Math**

The slope of Ax+By=C is -A/B This is because you can rearrange things, as in your case, to 5x+2y = 20 2y = -5x + 20 y = -5/2 x + 10 This is the slope-intercept form, and you can easily see that the slope is -5/2.
*October 8, 2014*

**Math**

since x is the horizontal axis, and y is the vertical axis, the rise is obviously the change in y So, the run is the change in x
*October 8, 2014*

**pre calc**

well, just plug it in: 33/4 - 9x/2 = (-9x^3-6x^2-x+3)/(2x^2+5x+2) http://www.wolframalpha.com/input/?i=solve+33%2F4+-+9x%2F2+%3D+%28-9x^3-6x^2-x%2B3%29%2F%282x^2%2B5x%2B2%29
*October 8, 2014*

**Homework (Math)**

recall that 1/i = -i So, you have (1-2i)/(2i) = (1/2)(1/i) - 1 ...
*October 8, 2014*

**Math! Please check!**

We have a winner!!
*October 8, 2014*

**Math! Please check!**

So, HI=(I-H) = 14-8 = 6 GM = M-G, so M-1 = 6 or 1-M = 6
*October 8, 2014*

**Math**

good work.
*October 8, 2014*

**Math**

7(-6) - 5(-14) = -42 + 70 = 28 ok What about the others? You have not found them all yet.
*October 8, 2014*

**Math: ALGEBRA**

a+b = a+xy b = xy x = b/y try the others. First get all the w or r terms on one side, then factor it out and divide by what's left.
*October 8, 2014*

**ap calc**

2x - (x^2+4)/x = 0 2x^2 - x^2 - 4 = 0 x^2 - 4 = 0 x = -2 or 2 Now, find y at those values, and those are the horizontal tangents.
*October 8, 2014*

**ap calc**

you know that y^2 = (x^2+4)/x, so just plug that in and solve for x.
*October 8, 2014*

**ap calc**

Assuming you meant y= (ax+b)/((x-1)(x-4)) y' = (ax^2+2bx-(4a+5b))/((x-1)(x-4))^2 Now, y'=0 when ax^2+2bx-(4a+5b) = 0 when x=2, that means 4a+4b-4a-5b=0 b=0 So, y = ax/((x-1)(x-4)) at x=2, y=-1, so 2a/-2 = -1 a = 1 and so y = x/((x-1)(x-4))
*October 8, 2014*

**ap calc**

So far, so good. We know that for a horizontal tangent, y'=0, so 2x-y^2 = 0 But, we already know that y^2 = (x^2+4)/x, so 2x - (x^2+4)/x = 0 2x^2 - x^2-4 = 0 x^2 = 4 x = 2 or -2 At x = 2, y = 4 At x = -2, y = -4 Those are the horizontal tangents
*October 8, 2014*

**geometry**

2(x+y) = 22 x+y=11 So, just list the pairs of numbers which add up to 11.
*October 8, 2014*

**Math @Reiny**

Recall that since i^2 = -1, 1/i = -i (1-2i)/(2i) = 1/(2i) - (2i)/(2i) = 1/2 (-i) - 1 = -1 - 1/2 i
*October 8, 2014*

**math help**

well, just multiply it out: 12*11*10*9*8
*October 8, 2014*

**Pre-calc/Trig...**

correct.
*October 8, 2014*

**Pre-calc/Trig...**

a polynomial of degree 2 is a quadratic.
*October 8, 2014*

**Calculus I**

since sin^2 = 1-cos^2 and cos(2x) = 2cos^2 - 1, 2cos^2 - 1 - cos = -1+cos^2 - 1/4 cos^2 - cos + 1/4 = 0 (cos - 1/2)^2 = 0 cos = 1/2 x = pi/3 or 5pi/3
*October 8, 2014*

**CALCULUS HELP NEEDED ASAP!**

Oops. Do you see my mistake? Hint: C is wrong.
*October 8, 2014*

**CALCULUS HELP NEEDED ASAP!**

period of sin(kx) or cos(kx) is 2π/k. SO, for a period of 2 seconds, k = π. V(t) = A cos(πt)+C residual volume is 1150, so V(t) = A cos(πt) + 1150 Tidal volume is 3200, so V(t) = 1600 cos(πt) + 1150 Since cos has max at t=0, we are done.
*October 8, 2014*

**Math-trigonometry**

(a) max: d^2 = 192^2 + 71.6^2 min: d^2 = 192^2 + 8.1^2 (a) max: tanθ = 192/8.1 min: tanθ = 192/71.6 Didja forget your Pythagorean Theorem and the definitions of the basic trig functions?
*October 8, 2014*

**Algebra 2**

can you say "google?" It took me about 10 seconds to find a site that can generate nice printable number lines.
*October 8, 2014*

**math (need check answer)**

Ty I am not sure what you mean by swapping. Q1 asked for the algebraic expression which is x + y Q2 has actual amounts of balloons so now these should be added to the original formula 14x + 8y where x = $3 and y = $4 Therefore 14*3 + 8*4 = $74
*October 8, 2014*

**Not Me, Wrong Answer**

The curse of not having used a less common name.
*October 8, 2014*

**math (need check answer)**

I think the answer to Q1 is simply x + y
*October 8, 2014*

**caculus**

Using similar triangles, if the shadow's length is s and the woman is x away from the light, s/1.5 = (x+s)/6 That should help, eh?
*October 8, 2014*

**caculus**

a woman 1.5 tall walks at a rate of 1.2m/s directly away from the street light that is 6m above the street. At what rate is her shadow changing?
*October 8, 2014*

**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*

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