Wednesday
May 4, 2016

Posts by steve

Total # Posts: 40,164

Math
h(t) = 1 + vt - 16t^2 max height is reached at t = v/32, so 1 + v(v/32) - 16(v/32)^2 = 35 v = 8√34 h(t) = 1 + 8√34 t - 16t^2 h=0 at t=2.94 v(t) = 8√34 - 32t, so when h=0, v = 8√34 - 32(2.94) = -47.43 ft/s
April 18, 2016

Trigonometry
well, geez, just solve the equation. r = v^2sin2θ/g 1/32 1200^2sin(2θ) = 3000 sin2θ = (32*3000)/1200^2 = 1/15 Of course, there are two solutions, since sinθ is positive in [0,pi]. But you want the minimum value.
April 18, 2016

Math
clearly the answer cannot be 1, since that would mean you always get tails or roll less than 4. there are 12 possible outcomes, easy to list them. 1/2 give tails 1/2 * 3/6 = 1/4 gives heads and n<4. 1/2 + 1/4 = 3/4 or, consider P(heads & n>=4) = 1/2 * 1/2 = 1/4 you want ...
April 18, 2016

math
1.00 = 100% decrease by 17% leaves 83% = 0.83
April 18, 2016

Precalculus
consider the circle r = 2cosθ that is (x-1)^2+y^2 = 1 clearly r = 2scosθ is just a scaled up version of that. (x - s)^2 + y^2 = s^2 r = 2scos(θ+t) is just a rotated version, turned through angle t. Since t can be anything from 0 to 2pi, the center of our circle ...
April 18, 2016

Math
(3cm)^3 * 6 = 27*6 cm^3 = 162 cm^3
April 18, 2016

Math
that will be 1/2 + 1/2 * 1/6 = 1/2 + 1/12 = 7/12 you want P(heads OR (tails and n=3))
April 18, 2016

math
(x,y) -> (-x,y) so, just change the sign of the x-coordinates.
April 18, 2016

Math
parallel? I think not. They are the same line. Any solution to one also fits the other.
April 18, 2016

Trig
or island B
April 18, 2016

Math
width=w length=2w-5 perimeter: 2(w+l) = 2(w+2w-5) = 2(3w-5) = 6w-15 area: wl = w(2w-5) = 2w^2-10w that wasn't so hard, now, was it?
April 18, 2016

math
nope. sqrt(256) = 16 A is all irrational. and that's pi, not pie!
April 18, 2016

Trig
no cosine. the hypotenuse does not come into the calculation.
April 18, 2016

Trig
you draw a picture fer pete's sake! Then, having reviewed your basic trig functions, you will see that the height h is found from h/60 = cot35°
April 18, 2016

math
cube: 28^3 pyramid: (1/3)(28^2)(16) now just add 'em up
April 18, 2016

math
If train B's speed is x, then A's is x-6 Since time = distance/speed, 200/(x-6) = 230/x
April 18, 2016

Calculus
where did the 0 come from? also you cannot have cos and cos in f'.
April 18, 2016

Calculus
well, it's easy enough to see whether an answer is right. If f^-1(2) = x, then f(x) = 2 clearly not. It appears you want (f^-1)'(2) f'(x) = 7-3sinx+2cosx f'(2) = -3sin2+2cos2 (f^-1)'(2) = 1/f'(2)
April 18, 2016

calculus
nasty, until you note that f(x) = (x+1)/(2x+1) f'(x) = -1/(2x+1)^2
April 18, 2016

Math
see related questions below.
April 18, 2016

Trigonometry Help please
z^n = r^n cis(nθ)
April 18, 2016

math calculus
y = x^(2/3)(10-x) = 10x^(2/3) - x^(5/3) y' = (20/3)x^(-1/3) - (5/3)x^(2/3) = 5/3 (4-x)/x^(1/3) y'=0 when x=4 y increases when y'>0, or x<4 see the graph and info at http://www.wolframalpha.com/input/?i=x^%282%2F3%29%2810-x%29
April 18, 2016

Algebra
well, you need 3x+4 >= 0 at x=-4/3, y=-5, its minimum value.
April 18, 2016

math
You have seriously garbled the question. It looks like a straightforward law of cosines problem. The distance d is found using d^2 = 12^2+5^2 - 2*12*5 cos37°
April 18, 2016

Math
the 2nd equation is 0.04176x + 0.01782y = 0.01034 then since you have y, 0.04176x + 0.01782(0.4276-x) = 0.01034 0.02394x = 0.0027202 x = 0.1136
April 18, 2016

Algebra
make that Range = [-5,∞)
April 18, 2016

Algebra
I assume you mean y = 2√(3x+4)-5 the domain of √x is x >= 0, so here you must have 3x+4 >= 0 x >= -4/3 That is, the domain is [-4/3,∞) Since √(3x+4)=0 at x=-4/3, the range is [5,∞)
April 18, 2016

math
9Am, of course. But the watch shows 9:00AM - 0:2*48 = 7:24 AM
April 18, 2016

math p.s. is very hard
when x changes by 1, y changes by -5. So, the slope is -5 y = -5x + b Since when x=0, y=-1, y = -5x-1
April 18, 2016

Algerbra (Please help ASAP)
and F as well.
April 18, 2016

algebra
1/b - 1/a = 1/c - 1/b b-a = (c-4)-b b/a = (c-3)/b I get c=12
April 18, 2016

math- algebra 2
20000 * 1.05^13
April 18, 2016

Trigonometry
(3cis27°)^5 = 3^5 cis135° = 243 (1/√2 - 1/√2 i) (2cis40°)^6 = 2^6 cis240° = 64 (-1/2 - √3/2 i) you can make those into a+bi form, but you need to review deMoivre's formulas
April 18, 2016

Math
√(2x-4) + 5 = 7 √(2x-4) = 2 2x-4 = 4 x = 4 check: √(8-4) + 5 = 2+5 = 7
April 18, 2016

Pre calculus
just review your trig definitions cotx * secx = cosx/sinx * 1/cosx = 1/sinx
April 18, 2016

algebra
5n+10d+25q = 780 n+d+q = 46 n+d = q-2 Now just solve.
April 18, 2016

algebra
if $x at 6%, the rest (2150-x) is at 8%. So, now we have .08(2150-x) = 22+2(.06x) now just crank it out.
April 18, 2016

math
(a) find t where 1.011^t = 2
April 18, 2016

Math (Elementary Algebra)
2x^2 + 3xy - 4y^2 now substitute your values for every x and y: 2(2^2) + 3(2)(-4) - 4(-4)^2 = 2(4) - 24 - 4(16) = 8-24-64 = -80
April 18, 2016

calculus
I assume you are looking for the area. A straightforward integration will give the algebraic area, since the curves cross at x=1, and the area changes sign. ∫[-2,2] (-x^2+6x+2)-(2x^2+9x-4) dx = ∫[-2,2] -3x^2-3x+6 dx = 8 However, to get the geometric area, you need ...
April 18, 2016

Calculus
the curves intersect at 𝜋/6 and 5𝜋/6, so the volume, using shells, is v = ∫[π/6,5π/6] 2πrh dx where r=x and h=sinx - 1/2 v = ∫[π/6,5π/6] 2πx(sinx-1/2) dx = π^2(√3 - π/3) using discs, it's tougher: v...
April 18, 2016

Algebra
because the discriminant (b^2-4ac) is negative.
April 17, 2016

math
since time = distance/speed, 45/(x-2) + 45/(x+2) = 14
April 17, 2016

Math
you haven't paid much attention to the solutions to your previous problems. Review the distributive property. Then you will see that -2r(8r+5) = -2r(8r) + (-2r)(5) = -16r^2 - 10r
April 17, 2016

math
the height h is given by h/517 = tan 16°
April 17, 2016

Math
if you say so. Good luck with that.
April 17, 2016

Math
I showed the steps in the solution, not three answers. See those "=" signs? That means that each line is equal to the one above it, not a new answer. It just shows the way to simplify the expression.
April 17, 2016

Math
EXCUSE ME??? I showed you the answer. None of the choices matches. Check for typos in the problem or the answers offered.
April 17, 2016

Math
huh? really? 2a(a^2+4a) = 2a(a^2) + 2a(4a) = 2a^3 + 8a^2 check for typos...
April 17, 2016

Stats
you can play around with Z table stuff at http://davidmlane.com/hyperstat/z_table.html
April 17, 2016

mathematics-need help urgently please
v = x^2h, so h = 1000/x^2 a = 2x^2 + 4xh = 2x^2 + 4000/x da/dx = 4x - 4000/x^2 = 4(x^3-1000)/x^2 so, da/dx = 0 when x=10 a = 2*100 + 4*10*1000/100 = 600 as usual, area is minimum when the shape is a cube.
April 17, 2016

PRECALC
you know that anything more complicated than a quadratic is tough, so look for low-hanging roots: ±1,±2,±3. A little synthetic division yields P(x) = (x-3)(x+1)(x^2+1) now it's easy.
April 17, 2016

precalc
of course -b/2a does not work. It's not a quadratic. Furthermore, x = -b/2a gives the location of the vertex of a quadratic, not the roots. You know that any rational roots must be among ±1,±2,±5,±10 A little synthetic division shows that p(x...
April 17, 2016

precalc
d: the arccos has principal vales from 0 to π. cos(-4π/3) = -1/2 cos^-1(-1/2) = 2π/3 f: cos(13π/12) = -cos(π/12) = -x arccos(-x) = π-arccos(x) = 11π/12 The others look good. Be careful with the principal values stuff.
April 17, 2016

dividing fraction with brackets
5/6 - 2(-1 3/4)/(5 1/5) 5/6 - 2(-7/4)/(26/5) 5/6 - 2(-7/4)(5/26) 5/6 + 35/52 (5*32 + 35*6)/312 470/312 235/156
April 17, 2016

Math
r:b = 3:2 = 9:6 b:g = 3:7 = 6:14 r:b:g = 9:6:14 assuming none of the ones removed were red, 1/4 (9x+6x+14x - 7) = 9x Hmmm. I get x = -1 better double-check my math and the problem.
April 17, 2016

maths
by definition, x = arccos(3/5) of course, x might be in quadrants I or IV. cos(.9273) = 0.6 cos(5.3559) = 0.6 x = 2kπ ± 0.9273
April 17, 2016

Trigonometry
Draw your triangle in standard position. Then you have r=5 secθ = r/x = 5/-3
April 17, 2016

maths
The first digit must be 1,2 or 3 That leaves 4 digits to shuffle for the others. So, the total number is 3 * 4! = 72
April 17, 2016

calculus help
or, you can expand cos^10(x) as combinations of single powers of cosines: 512 cos^10(x) = 126 + 210cos(2x) + 120cos(4x) + 45cos(6x) + 10cos(8x) + cos(10x) those terms are easy to integrate. They come from repeated use of cos(2x) = 2 cos^2(x)-1 cos(4x) = 2cos^2(2x)-1 and so on.
April 17, 2016

calculus help
This has to be done in several steps using integration by parts. To see how it works, take a look at https://en.wikipedia.org/wiki/Integration_by_reduction_formulae
April 17, 2016

Calcus
oh. right. you want to use calculus. f' = 2x+k f'=0 at x = -k/2 f(-k/2) = k^2/4 + k(-k/2) + 2 = k^2/4 - k^2/2 + 2 = -k^2/4 + 2 we want the minimum to be 1, so -k^2/4 + 2 = 1 k^2/4 = 1 k^2 = 4 k = ±2 as above
April 17, 2016

Calcus
try completing the square. x^2+kx+2 = x^2 + kx + (k/2)^2 + 2 -(k/2)^2 = (x + k/2) + 2 - k^2/4 Now you have the vertex form of the parabola, with the vertex at x = -k/2. At that point, the minimum is 2 - k^2/4 So, now just set 2 - k^2/4 = 1 k^2/4 = 1 k^2 = 4 k = ±2 f(x...
April 17, 2016

HUNGER GAMES
google is your friend
April 17, 2016

algebra
oops. |2n+1| = (2n+1) or -(2n+1) if -(2n+1) = 19 -2n = 20 n = -10 check: |(3(-10)+1-(-10)| = |-30+1+10| = |-19| = 19
April 17, 2016

math
I think it's supposed to read "1/3 of them are blue." 1/3 of 21 = 7
April 17, 2016

Calculus
as usual, the volumes can be done using shells (v = 2πrh) or discs (washers) (v=πr^2), both multiplied by the thickness (dx or dy). I'll show both integrals (i) v = ∫[0,ln3] π(e^(2x))^2 dx = 20π v = π(1^2)(ln3) + ∫[1,9] 2πy(ln3 - 1...
April 17, 2016

math
that's alpha and beta. I'll use x and y for ease of typing. since the angles are complementary, cos(x) = sin(y) cos(x)*cos(y) = sin(y)*cos(y) = 1/2 sin(2y) since sin has maximum value of 1, ...
April 17, 2016

MATHS
times D w by D h by D l
April 17, 2016

math
1 - 3/7 = 4/7
April 17, 2016

Math
3(-1) / ((-1)^2-(-1)-12) = -3/-10 = 3/10 = 0.3 you are correct
April 16, 2016

algebra
since time = distance/speed, if his original speed was x, 90/x + 90/(2x) = 3 x = 45
April 16, 2016

math
if the original cost is c, and her selling price is p, then .90p = .81c * 1.20 p = 1.08c or, 8% more than the original price
April 16, 2016

Math
as with all circles, C = 2πr
April 16, 2016

Math
ATT: c(m) = 12.00 for m <= 250 12.00 + .05(m-250) for m>250 T Mobile: c(m) = 3.00 for m <= 30 3.00 + .10(m-30) for m > 30 Virgin: c(m) = 20.00 for m <= 400 20.00 + .10(m-400) for m>400 Now just figure the cost for various amounts of minutes, especially where ...
April 16, 2016

math
did that two hours ago: http://www.jiskha.com/display.cgi?id=1460822853
April 16, 2016

Math
u = 4n 19n+9u = 7500
April 16, 2016

math
(7 -3)(x) = (21) (5 -1)(y)   (85) formatting not good here.
April 16, 2016

math
x+y = 600 1.22x + 1.08y = 600
April 16, 2016

Algebra
well, f(x) = (5x-1)(x+1) when is that zero?
April 16, 2016

maths help polynomial agn
how does all that stuff on the left relate to 1.004? In any case, just use your calculator. or, type it in at google. (2+√3)^6+(2-√3)^6 = 2702
April 16, 2016

Maths help - not polynomial
this is not a polynomial. It is just an expression. 4^5 - √5^5 = 4^5 - 25√5 not much to do with that. I suspect a typo
April 16, 2016

Math
(1/2)(3x)(x+7) = 66 now just expand and solve for x. Then the height is x+7.
April 16, 2016

Math
y = 1/x zx = 12/35 zy = 15/7 zx = 12/35 z/x = 15/7 12/(35x) = 15x/7 84 = 525x^2 x^2 = 84/525 = 4/25 x = 2/5 y = 5/2 z = 6/7
April 16, 2016

Math (Geometry)
the exterior angles always sum to 360.
April 16, 2016

Calculus (Im I Doing This Right???? Im Unsure)
either way works fine. Plug in the point before or after. The first way gets you to 4x-6, and then you can use that to find the slope at any point, without having to go through all of the steps each time.
April 16, 2016

Alegebra
the area increases as the square of the linear scale factor. So, it would increase by a factor of 1.10^2
April 16, 2016

Further math
n/2 (2*4 + (n-1)*3) = 209 1/2 (3n^2+5n) = 209 3n^2+5n-418 = 0 (3n+38)(n-11) = 0 n=11
April 16, 2016

maths help me!!!
you have several values, each of which has two cases. |x+1| = x+1 if (x+1) >= 0 |x+1| = -(x+1) if (x+1) < 0 So, you need to set up the inequalities and check both values for each || quantity. As a help, see the graphs at http://www.wolframalpha.com/input/?i=|x%2B1|-|x|%...
April 16, 2016

Math
20ml = 0.02L, so 37800L / (.02L/s) = 1,890,000 seconds = 21 days 21 hrs
April 16, 2016

Math
x * 1.10 * 1.15 = 10120
April 16, 2016

Algebra 2
describe the diagram. Whatever the layout, I'm sure the maximum area will be when the fence is divided equally among lengths and widths.
April 16, 2016

maths (jnv arihant) work and time
in 20 days, only 60/132 = 15/33 of the wall is done. So, that means each man has done 15/528 of the job. So, 18/33 remains. At this point, I get confused. What does working 6 as many hrs mean? Surely they cannot be working 6 times as many hours. Anyway, see what you can do ...
April 16, 2016

Algebra 2
well, just solve -16t^2 + 40t + 6 = 10 You'll get two answers, one going up and one coming back down.
April 16, 2016

math
(3n+4)/(n+2) = 3 - 2/(n+2) So, if n=0, that's 3 - 2/2 = 2 n = -1, it's 3 - 2/(-1) = 4 If n is any other value, the fraction is not an integer.
April 16, 2016

maths
if BC and CA are lines, then the locus of points equidistant from both lines is the bisector of the angle between them.
April 16, 2016

maths
not sure what "partly" means, but if direct, then y = k√x, so k=1, and y=√x If inverse, then y=k/√x so k=1, y=1/√x
April 16, 2016

maths
The distance from (1,2) to the line 3x-4y-2=0 is |3*1-4*2-2|/√(3^2+4^2) = 7/5 If the parabola is expressed in the form y^2 = 4ax, then the distance from the directrix to the vertex is a. So, 4a = 28/5
April 16, 2016

math
a = 3w^2 + 2(wh + 3wh) = 3w^2+8wh since a=3600, h = (3600-3w^2)/8w The volume is 3w^2h = 3w/8 (3600-3w^2) find the derivative, set it to zero, and you will find that w=20. So, h=15 and the maximum volume is 20x60x15 = 18000
April 16, 2016

Math
75 - x/2 - 6 = 32
April 15, 2016

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