Friday
May 22, 2015

Posts by Steve


Total # Posts: 31,325

Calculus
y = 1/(1+be^kt) y' = kbe^kt/(1+be^kt)^2 y' will be greatest when y" = 0 y" = k^2be^kt(3e^kt-1)/(1+be^kt)^3 so, that will be when t = -1/k ln3 In this case, when t = 1.48
April 9, 2015

Earth Science
thank you
April 9, 2015

Earth Science
Which of the following are you most likely to experience a-total solar eclipse b-total lunar eclipse c-full moon d-partial lunar eclipse? my answer is full moon
April 9, 2015

Math
A is what you want B is just y = 8x C is y = (12-4)x D is y = 12x - 12*4 = 12(x-4)
April 9, 2015

Calculus
f(x) = √(2x) g(x) = f^-1(x) = x^2/2 f'(x) = 1/√(2x) g'(x) = x So, we want 1/√(2c) = c 1/2c = c^2 1/2 = c^3 c = (1/2)^(1/3)
April 9, 2015

Calc AB
clearly, since f'(-3) = 0, f^-1 has a vertical tangent at x = f^-1(-3) = 2.
April 9, 2015

Calc AB
Looks like D to me
April 9, 2015

Calc AB
Hint: dx/dy = 1/(dy/dx)
April 9, 2015

Calculus AB
well, f^-1(x) = 9-x^2, so ...
April 9, 2015

Chem
Volume of nitrogen gas is 125ml atmospheric pressure is 763mm Hg the water temperature inside the eudiometer is the same as the level of the water in the beaker. Calculate the volume if the nitrogen at STP. P1V1/T1=P2V2/T2
April 9, 2015

Calc
that is just the integral of 3x^-6 - 4|x| just use your power rule.
April 9, 2015

Integral
just use the power rule on u^(-5/4) + 5.5 u^(1/2) du
April 9, 2015

Calculus
y=2x xyz=k, so z=k/2x^2 the cost c is c(x,y,z) = 6xy + 10(2xz + 2yz) c(x) = 6x(2x) + 20(3x)(k/2x^2) = 12x^2 + 30k/x
April 9, 2015

math (explanation and answer)
The circumference of the original paper is 2πR If the arc AB subtends an angle θ, then the circumference of the cone formed is 2πR - Rθ = R(2π-θ) So, the radius of the cone is r = R(1-θ/2π) Since the slant height of the cone is still r, ...
April 9, 2015

math
y=3
April 9, 2015

calculus (please with steps and explanations)
This was done by Damon, but here's my take ∫[0,5](f(x)+2) dx = ∫[0,5] f(x) dx + ∫[0,5] 2 dx = 4 + 2x[0,5] = 4 + 10 = 14 Since we are dealing with an even function, ∫[-5,5] f(x) dx = 2∫[0,5] f(x) dx = 2*4 = 8
April 9, 2015

Calculus
I can't see the diagram, but it appears that if the shadow is x, then 25/x = tanθ so, -25/x^2 dx/dt = sec^2θ dθ/dt -25/2500 dx/dt = (1+1/4)(-1/4 * π/180) Now just solve for dx/dt
April 9, 2015

Algebra 1
well, since they are usually written as y = a * b^x it seems pretty clear, wouldn't you say?
April 8, 2015

physics
If the first object takes t seconds to hit, h - 4.9t^2 = 0 t = √(h/4.9) the second object is thus h-4.9(t-1)^2 = 20 h = 31.63 m
April 8, 2015

Math
Thomas put 1/4 of the c coins he had in his pocket into the jar under his bed. He put 16 coins into the jar. The equation that models this situation is 1/4c = 16. How many coins did Thomas have in his pocket? a 4 coins b 12 coins c 20 coins d 64 coins The answer would be c.
April 8, 2015

AP CALC
since x^2+y^2+z^2 = 4 using symmetry, we can take 8 times the volume in the first octant. Then v = 8∫[0,2] ∫[0,√(4-x^2)] ∫[0,√(4-x^2-y^2)] dz dy dx
April 8, 2015

Math
no. rays might be parallel such an angle of zero measure could be said to fit the constraints, but that might not be allowed.
April 8, 2015

calculus
assuming an open box, then x^2 + 4xz = 426 v = x^2 z = x^2 (426-x^2)/4x = 426x - x^3
April 8, 2015

Math didn't post problem right
find the Quotient: 1,754/21 a 1733 b 21 11/83 c 83 11/21 d 1775 Is C the correct answer. I had post the problem wrong. Sorry
April 8, 2015

Math
find the quotient: 1,754/12 a 1733 b 21 11/83 c 83 11/21 d 1775 Would C be the correct answer?
April 8, 2015

Math
I agree.
April 8, 2015

Math
The determinant |2 6| |1 3| = 6-6 = 0 So, there is no inverse
April 8, 2015

Algebra
Better think again, S. the line x=4 is a vertical line The vertical line through (-6,-2) is x = -6
April 8, 2015

Algebra 2 math
the triangle's 3rd side is √(41^2-40^2) = 9 So, now you know all three sides, and the angles, so the trig functions are easy to read off. sin G = 9/41 and so on
April 8, 2015

linear algebra-urgent
you know p. Can you not figure its length? √(33^2+44^2) = 55
April 8, 2015

linear algebra-urgent
#1 a unit vector in the direction of w is z=[3/5;4/5] p = u.z = 11/5 z = [33/25;44/25] = [1.32;1.76] you are correct |kp| = k|p| = 55/25 k So, k = 25/55 As for the span, that is usually defined for a set of vectors. span{w} would just be w. So, any vector orthogonal to w will ...
April 8, 2015

math
54.2/16 * 2.31
April 8, 2015

math
Not even close. The area is length * width, or 8(6x+3) = 48x+24 6x+3 is not 9x. Even if it were, 9x+8 would be half of the perimeter, not the area.
April 8, 2015

Geometry
wrong. The two circular ends of the cylinder are usually parallel. I guess that leaves only one other possibility, right?
April 8, 2015

math
well, just start listing them: 3568 3586 ... 8653 There are only 24 of them.
April 8, 2015

Algebra
If Nathan is x and Nicole is y, we have y = 2/3 x (y-2) = 1/2 (x+5) Now just solve for x.
April 8, 2015

Math (Please help ASAP)
It's just a quadratic in p: q+p^2-33p = 9 p^2 - 33p + (q-9) = 0 Now just use the quadratic formula to get the two values for p.
April 8, 2015

Math
1/3 (9x-2) + 1 = 2(4x+1) You can multiply by 3 to get 9x-2 + 3 = 6(4x+1) 9x+1 = 24x+6 -5 = 15x x = -1/3
April 8, 2015

chemistry
CuS + 2HNO3 = Cu(NO3)2 + H2S That should help, right?
April 8, 2015

trigonometry
speed = distance/time, so 2π*3960mi/24hr = ? mi/hr 2πrad/24hr = ? rad/hr
April 8, 2015

trigonometry
v = 2π*14in/rev * (.5/2π)rev/s = 28 in/s .5rad/s * 1rev/2πrad * 60s/min = 4.77 rev/min .5rad/s * 180°/πrad = 90/π °/s
April 8, 2015

maths
this is just an A.P. with d = 4 a = 100-20*4 = 20 So, the sum of 21 rows is S = 21/2 (20+100)
April 8, 2015

math
draw your triangle the other side is √15 since we are in QII and sin is positive, x = -√15 y = 1 r = 4 so, cosx = -√15/4 Now use those values to plug into your half-angle formulas.
April 8, 2015

Pre-calc
Or, you can go the other way sin(7x) = sin(6x)cos(x) + cos(6x)sin(x) and start expanding those as well, till all you have left is a bunch of sin(kx).
April 7, 2015

Pre-calc
http://www.wolframalpha.com/input/?i=%28sinx%29%5E7 will show the answer you need. sin^7 = sin(1-cos^2)^3 Now you can start expanding and using the sum formulas. I'm sure a google search will show up all the gory details.
April 7, 2015

math
why use } when / is available? (4/9)(1/8) = 1/18 (1/18)(1/3) = 1/54
April 7, 2015

Math
correct.
April 7, 2015

Math
There is clearly a typo in the above, since the function is a parabola which opens upward, and so has no maximum. If we go with y = -6x^2+42x-60 then that works out to y = -6(x^2-7x+10) = -6(x-5)(x-2) The vertex is at x = 3.5, so that means 3500 boards. You know, if you keep ...
April 7, 2015

Math
-5x^2 - 30.5x = -1/10 (50x^2 - 305x) = -5/10 x (10x-61) I suspect a typo, since the roots of the above are clearly 0 and 6.1
April 7, 2015

Math
no, it can be any real number.
April 7, 2015

Calculus
see the related questions below.
April 7, 2015

math
I'd think so, since the eye perceives the linear dimensions, which grow much more slowly than the volumes.
April 7, 2015

I NEED HELP WITH THIS
how far do you get? Do you not have any ideas? If not, you'd better review the textbook where it discusses this. To start, A series: R = r+r+r parallel: 1/R = 1/r + 1/r + 1/r
April 7, 2015

grammar
I agree with (a) I think if it had said each delegate and each alternate, then (b) would be better.
April 7, 2015

math
you ought to explain what "1 } 10" means.
April 7, 2015

math
P is the same as if there were a 5-section wheel with just the numbers 1-5.
April 7, 2015

Math
you mean you can figure out 2*3+5, but you cannot do the same for 1,2,4? Ai caramba!
April 7, 2015

Algebra
A: LW = √18√24 = √(18*24) = √(2*3^2 * 2^3*3) = √(2^4 3^3) = 12√3 since A = LW, what if you have (L/2)(W/2)?
April 7, 2015

geometry
without some kind of explanation of the angles and the diagram, I don't think you can get much help here. By the way, ≅ is congruent. Rather than describing the symbol, why not just say congruent? And your opening sentence is bogus, since you don't say what <1...
April 7, 2015

math help
F is undefined where the denominator is zero #2 ? #3 domain is all reals except for the undefined value(s) #4 y-intercept (at x=0): -6/(0-3) -1 = -6/-3 - 1 = 2-1 = 1 x-intercept (at y=0) -6/(x-3)-1 = 0 -6 - (x-3) = 0 -6-x+3 = 0 x = -3
April 7, 2015

Math
well, 12^2 = 144, so you want 6x+6 = 12 or 6x+6 = -12
April 7, 2015

Math
#1 √(x+4)-3 >= 4 √(x+4) >= 7 x+4 >= 49 x >= 53 #2 t = √(d/16), so we want (using t in seconds) √(d/16) > 60 d/16 > 3600 d > 57600
April 7, 2015

Math
(2w+a)^8 = ... + 16wa^7 + ... (-x+b)^7 = ... - 35x^3b^4 (y-2z)^4 = ... + 24y^2z^2 So, I get -13440wx^3y^2z^2
April 7, 2015

science.......
(a) 60W * 1 hr = 60 Wh (b) .060 kWh * .1745 $/kWh = 0.01 200kJ/270s = 740W
April 7, 2015

math
well, how many points in the empty set?
April 7, 2015

UNISA
to accrue to how much?
April 7, 2015

math
If I interpreted the rather garbled English, you want x and y where x+y = 44 xy = 1280
April 7, 2015

math
eliminate z and you have 100-x-y = 200-10x-2y 9x+y = 100 So, you could let x=10, y=10, that would make z=80 Or, you could have x=1,y=91, so z=8 There is no unique solution.
April 7, 2015

algebra
I think you need some parentheses in that horrid run-on expression. As written it could mean x^2 - 9y^2/xy / 1/y - 3/x = x^2 - 9y/x * y/1 - 3/x = x^2 - 9y^2/x - 3/x = x^2 - 3(3y^2+1)/x There are, of course, many other ways to parse all that stuffed jammed together. Unless ...
April 7, 2015

science 1 question
ahem. it does not form energy by spinning. It changes electrical energy into kinetic energy (of motion).
April 6, 2015

science 1 question
do you feel sucked into the fan when you turn it on? Does it feel like when an elevator starts? That's gravitational. Hint: what the heck does a fan do when you turn it on?
April 6, 2015

Math
well, ya got a table? Maybe these graphs will help you out in determining the transformations required. http://www.wolframalpha.com/input/?i=plot+y%3D3%5Ex%2C+y%3D3%5E%28%E2%88%92%28x%2B1%29%29+%E2%88%922
April 6, 2015

Calculus
Just curious. How do you get from 2(2)dy/dt+(2)(-1)(-4)+6(-1)^2=0 to 10 dy/dt+8=0 ???
April 6, 2015

Calculus
Assuming you mean c^2 = x^2 + 98√(x+57) then c^2(4) = 4^2 + 98√61 = 16+98√61 c(4) = 27.95 2c dc/dx = 2x + 49/√(x+57) at x=4, we have 55.90 dc/dx = 8+49/√61 dc/dx = 0.255 Of course, I might have misread the function, with all those pesky words ...
April 6, 2015

Chemistry
(a) you are diluting the concentration by a factor of 6/.25=24 So, you will need 20/24 ml of 6M solution to produce 20ml of .25M solution. The rest, of course, is water. Do the others in like wise.
April 6, 2015

Calculus
Hmm. Ignore my previous comment. Still, if the functions are as given, Reiny's answer appears correct. Are there mis-types somewhere?
April 6, 2015

Calculus
well, what is P? That is the rate you are calculating.
April 6, 2015

1 question omh help??
Looks like C to me.
April 6, 2015

intermediate algebra
Hmm. I get (3(x-3) - x(x+3) + 1(x-3)(x-3)) / ((x-3)(x-3)(x+3))
April 6, 2015

Physics
momentum must be conserved: 1*3 + 2*0 = (1+2)v Although, I fail to see how they could properly roll, if sticking together after such a collision.
April 6, 2015

Physics
assuming the original mass was really 20.0 kg, total momentum must remain at zero, so 15.0*2 + 5.0v = 0
April 6, 2015

Pre-Calculus
not quite. since (x+a)^2 = x^2+2ax+a^2, x^2+9x = x^2+9x+(9/2)^2-(9/2)^2 x^2+9x+20 = (x + 9/2)^2 + 20-81/4 = (x + 9/2)^2 + 319/4
April 6, 2015

calc
f = 2x+15-19e^x f' = 2-19e^x f'(0) = 2-19 = -17 so, the tangent line is y+4 = -17(x-0) see the graphs at http://www.wolframalpha.com/input/?i=plot+y%3D2x%2B15-19e%5Ex%2C+y%3D-17x-4
April 6, 2015

calc
x = e^(8-p) revenue is x*p = pe^(8-p) profit = revenue-cost = xp-x = x(p-1) = (p-1)e^(8-p) so, if y is the profit at price p, dy/dp = (2-p)e^(8-p) set the price at p=2
April 6, 2015

chemistry
if you mean g/L, that would be 1mole/22.4L = 0.759 g/L
April 6, 2015

Calculus
well, geez, just plug in e^2 into f'(x) f'(e^2) = 4(ln(e^2))^3/e^2 = 4(2)^3/e^2 = 32/e^2 remember ln(e^u) = u e^(ln u) = u
April 6, 2015

algebra
what is that 4 doing there? is 4√y supposed to mean 4th root of y? x^(11/10) is 10th-root(x^11)
April 6, 2015

math
man, look up your point-slope formula: y-5 = 2/3 (x+1)
April 6, 2015

geometry
transitive: A≅B and B≅C ==> A≅C No idea what the diagram shows.
April 6, 2015

geometry
M=(A+B)/2 clearly AM=MB = 1/2 AB Look up your distance formula to figure length of AB.
April 6, 2015

Calculus 2 (Series)
see the solution here: http://www.math.ucla.edu/~hendricks/CalculusIISummer2011/calc2practicefinalsolutions.pdf
April 6, 2015

math
5f+4s = 14.80 (3/4)f = (3/5)s s = 1.85
April 6, 2015

maths
before: TTT after: TTT TTT so, how many T's?
April 6, 2015

Differential Equation 4
no ideas on these problems? Homework dumps are discouraged.
April 6, 2015

Differential Equation 3
why the stupid carets? These are not exponents. (x^2+1)y"+2xy'=0 Since y = c1 + c2 arctan(x) I suspect you can now come up with the series.
April 6, 2015

algebra
that copy/paste stuff will kill ya every time!
April 6, 2015

calculus
v(t) = ds/dt = 128-32t So, plug in t=4.
April 6, 2015

math
for m months, the cost c is c = 127 + 28m now plug in m=9 for the cost of 9 months. actually, c is the cost of joining and then using the club. The question is poorly worded.
April 6, 2015

Precal
so, if u=3^x, you have u^2 - 4u + 3 = 0 You can handle that, I presume?
April 6, 2015

calculus
wrong h = 130 + 35t - 16t^2
April 6, 2015

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