Saturday

December 20, 2014

December 20, 2014

Total # Posts: 27,647

**math**

Depends - do they tip on the whole bill? Most folks do. In that case, they spent $56.25 * 1.15 if the tax is included in the bill, as is usually the case.
*October 12, 2014*

**geometry**

I just did! The line AB has slope -5. So, any line parallel AB also has slope -5. The line you want is thus y-1 = -5(x+2)
*October 12, 2014*

**geometry**

a line with slope m containing (h,k) is y-k = m(x-h) Now plug in your values.
*October 12, 2014*

**precalc**

220/360 of the full circumference
*October 12, 2014*

**Algebra**

clearly, for a physical cube, the sides cannot be zero or negative. So, the domain is all positive real values: s > 0 So, the range, 6s^2, is also all positive reals, A > 0 Your teacher has further restricted the domain to s >= 5 So, the range 6s^2 >= 150 In ...
*October 12, 2014*

**Algebra**

the domain of all polynomials is all real numbers. Naturally, in the real world, only positive time makes sense, so the domain here is just t >= 0 What planet is this ball on? gravity on earth wold make the function H(t) = 72t - 16t^2 Find the vertex of that parabola. That ...
*October 12, 2014*

**college intermediate**

If x are taking both biology and Spanish, then 36+52-x = 200-126 x = 14 So, 36-14=22 are taking biology but not Spanish. That should get you started.
*October 12, 2014*

**Math**

If x = |x|, then x is positive If x-2 ≠ |x-2| then x-2 is negative That should get you started.
*October 12, 2014*

**Algebra 2 Answer Check (Reiny)**

You have done a horizontal compression
*October 12, 2014*

**Algebra**

f+s+t = 490 3f+2s+t = 878 s = 4+2t Now you can solve for f,s,t.
*October 12, 2014*

**Math**

as written, it is 0 with remainder x-6 I think you mean (10x^4-50x^3-800)/(x-6) See the details at calc101.com click on the "long division" button.
*October 12, 2014*

**Math**

If a rectangular array, 6x+6y = 750 a = 4xy = 4x(750-6x)/6 = 500x - 4x^2 max area at x = 62.5, y=62.5, large pen = 125x125 If a linear array, 8x+5y = 750 a = 4xy = 4x(750-8x)/5 = 600x - 32/5 x^2 max area at x=46 7/8, y=75, large pen = 186.5x75 As usual, the square provides the...
*October 12, 2014*

**AP CALC. AB**

#1 The particle is at rest when its velocity is zero. So, we need dx/dt=0 dx/dt = 6t^2-26t+22 So, solve for t #2 moving left ==> velocity is negative dx/dt = 16t^4-75t^2+60 So, solve for dx/dt < 0 #3 greatest speed is max velocity. That means dx/dt has a max, so d^2/dt^2...
*October 12, 2014*

**Algebra**

If the short leg is x, we have x^2 + (3x+13)^2 = (3x+14)^2 x = 9
*October 11, 2014*

**math**

the same as the number of places the decimal point has shifted.
*October 11, 2014*

**math**

Any value x such that 3.5-3.5 < x < 3.5+3.5
*October 11, 2014*

**Math (Algebraic Proving)**

Draw a diagram of an ellipse. Draw diagonals from (0,b) to (-c,0) and (c,0) The definition of such an ellipse is that the sum of the distances from a point to the foci is constant, and = 2a where a,b,c are described above. Just google any explanation of the definition of an ...
*October 11, 2014*

**math**

1.14c = s c = s/1.14 = .877s so, there is a 12.3% markup based on selling price.
*October 11, 2014*

**Algebra word problem**

clearly the equation of the arch is y = 20 - ax^2 y(18) = 0, so a = 0.0617 So, y = 20-0.0617x^2 y(9) = y(-9) = 15
*October 11, 2014*

**Math (Word Problem)**

The original square has side of length x. So, (x-8)(x-8)(4) = 576
*October 11, 2014*

**College Algebra**

rsx^2 + (rt+s^2)x + st = 0 Now just use the quadratic formula: x = [-(rt+s^2)±√((rt+s^2)^2 - 4rs^2t)]/2rs = [-(rt+s^2)±(rt-s^2))]/2rs = (-rt-s^2+rt-s^2)/2rs = -s/r or = (-rt-s^2-rt+s^2)/2rs = -t/s
*October 11, 2014*

**HELP!! Algebra**

the smaller the divisor, the larger the quotient. 12/6 = 2 12/4 = 3 12/3 = 4 12/2 = 6 12/1 = 12 12/(1/2) = 24 because there are 24 halves in 12 wholes. When dividing by a number less than 1, the quotient is larger than the dividend. Again, if a slice of pie is 1/6 of the pie, ...
*October 11, 2014*

**Math help**

yes. when dividing, it is the same as multiplying by the reciprocal.
*October 11, 2014*

**computer science**

64(mod 18) = 10 because 64 = 3*18 + 10 32+10 = 42
*October 11, 2014*

**Math**

ln(x+1)/ln(x-1) = 2 ln(x+1) = 2ln(x-1) x+1 = (x-1)^2 x+1 = x^2-2x+1 x^2-3x = 0 x = 0 or 3 check: ln(1)/ln(0) = 2 Not a solution ln(4)/ln(2) = 2 ln(2^2)/ln(2) = 2 2ln2/ln2 = 2 yes
*October 10, 2014*

**Math**

log(sqrt(x^2+1)) = 1/5 1/2 log(x^2+1) = 1/5 log(x^2+1) = 2/5 x^2+1 = e^(2/5) ...
*October 10, 2014*

**Math, Help Please IF you can**

(a) 5^2 = 25, and we want (3-h)^2 = 25 so, 3-h = ±5 g(x) = (x+2)^2 or (x-8)^2 (b) g(x) = x^2+16 (c) shift right 2 is (x-2)^2 Since (3-2)^2 = 1, g(x) (x-2)^2 + 24
*October 10, 2014*

**math**

or, (1 + 3 1/4) : (1 1/4 + 3 1/3) = (4/4 + 13/4) : (15/12 + 40/12) = 17/4 : 55/12 = (17*12):(4*55) = 204:220 = 51:55
*October 10, 2014*

**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*

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