Wednesday

November 26, 2014

November 26, 2014

Total # Posts: 27,019

**Math**

shift first by 4: x^3+4 then reflect: -(x^3+4) = -x^3-4 -x^3+4 is what you get when you reflect, then shift
*October 10, 2014*

**Math**

If m(n) = n^2/2 m(n-1.2) = (n-1.2)^2/2
*October 10, 2014*

**Algebra 2**

g(x) = f(x/(3/2)) = f(2/3 x) = |2/3 * 2x| - 3 = |4x/3| - 3 See http://www.wolframalpha.com/input/?i=plot+y%3D|2x|-3%2C+y%3D|4x%2F3|+-+3
*October 10, 2014*

**Algebra 2**

g(x) = f(x)/4 = |x/2| - 3/4 See http://www.wolframalpha.com/input/?i=plot+y%3D|2x|-3%2C+y%3D|x%2F2|+-+3%2F4
*October 10, 2014*

**math 11**

25000(1+.033)^4
*October 10, 2014*

**Math help 1 question!!!!!!!!**

C is correct. A is also, but if they are implying a square root of an integer, then it is false. After all, a/b = √(a^2/b^2) whatever values a and b have.
*October 10, 2014*

**Science**

well, the present date is 2014 So, what is 2014-(906±35)?
*October 10, 2014*

**Math**

-4 - √(4-x) = 6 -√(4-x) = 10 4-x = 100 x = -96 Unfortunately, this is not a solution, since -4 - √(100) = -4-10 = -14, NOT 6 √100 is NOT ±10. √100 is 10. So, the equation as written has no real solutions
*October 10, 2014*

**Math**

Just use Heron's formula: A = √((23)(23-12)(23-16)(23-18))
*October 10, 2014*

**Math**

If the angle is θ, the law of cosines says that 36^2 = 15^2 + 25^2 - (2)(15)(25) cosθ
*October 10, 2014*

**math**

Assuming that by "updated marks" you mean your average test score, and assuming that the tests are of equal weight, your average is just the average of the scores: (36+53)/2 Why do you append the sentence "It's my first test."? You just told us your ...
*October 10, 2014*

**math**

what, no calculator? 2(13.7) = 27.4 27.6/9.8 = 2.7959 √2.7959 = 1.672
*October 10, 2014*

**math**

present age of father = x 6 times the age of son = 6y so, we have x = 6y+5y I suspect you meant five more than If so, x=6y+5 If you meant five times as much as, then x=5*6y
*October 10, 2014*

**Math Help**

Not much engineering here. Must have been a test post.
*October 10, 2014*

**How long will it take the investment to double?**

The initial amount does not matter. You want e^0.048t = 2 t = ln2/0.048 = ?
*October 10, 2014*

**math**

f+200m = 122 f+189m = 118.15 Now subtract; the f's go away and you have 11m = 3.85 m = 0.35 Now, I expect you can find f, the flat fee.
*October 10, 2014*

**physics**

starting momentum: 1500*36 final momentum: 1500*72 That gives you momentum in kg-km/hr you probably want it in kg-m/s, so you need to convert km/hr to m/s.
*October 10, 2014*

**algebra2**

I don't see any fractions. How can there be a denominator?
*October 10, 2014*

**calculus**

I think you mean find the second derivative. Do you mean partial derivatives? There are three. Fx = 2e^y + 3ye^-x Fy = 2xe^y - 3e^-x Fxx = -3ye^-x Fyy = 2xe^y Fxy = Fyx = 2e^y + 3e^-x
*October 10, 2014*

**geometry**

three non-collinear points determine a plane. So, take any 2 on the first line, and any other from the second line. We know the lines are not skew, so they do determine a plane.
*October 9, 2014*

**Math**

10^7 > 10^6, so A and C are out. Now, which number is smaller than 1.8? 1.1 or 6?
*October 9, 2014*

**maths**

Assuming that in fact each compartment only holds 14 people, then since 387/14 = 27.6, we have 387 - 14*27 = 9
*October 9, 2014*

**Math**

how about 3,3 - 0,1 = 3,2 Something tells me that's not what you had in mind, but you don't give much to go on.
*October 9, 2014*

**Math**

just google point-slope form. Lots of explanations out there. I can't believe you are asking this question without having covered linear equations.
*October 9, 2014*

**Math**

assuming you want the equation for the line though the points (0,5) and (-3,-4), note that the slope of such a line is 3. So, using the point-slope form of the line, you have y-5 = 3(x-0) or y = 3x+5 Or, using the other point, y+4 = 3(x+3) y = 3x+5
*October 9, 2014*

**Math help Please**

well, a common right triangle is 5-12-13. Not sure just how things are set up, since you just give two sides of the table cloth and don't say anything about the third side.
*October 9, 2014*

**Math**

Let the numbers be x,x+2 and x+4. x^2 + (x+2)^2 = (x+4)^2 - 7 x = 5 check: 25+49 = 81-7 yes
*October 9, 2014*

**Math**

c+2s = 10 3c+2s = 18 so, 2c = 8 c = 4 s = 3 c+s = $7
*October 9, 2014*

**Algebra**

hey, come on. Surely you can do -3(3y-4)+4y = -3 -9y + 12 + 4y = -3 -5y = -15 y = 3 Now, x = 3y-4 = 9-4 = 5 Now do #2 the same way.
*October 9, 2014*

**Algebra**

Before posting this problem again, take a look at just what you have written. DON'T MAKE A NEW POST. Just fix the mistakes as a new reply to this one! You have given no details about the options. Always review your posting after it is done, and see what the heck you have ...
*October 9, 2014*

**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*

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