Wednesday
November 26, 2014

Posts by steve


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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