Friday
December 9, 2016

Posts by Steve

Total # Posts: 47,015

calculus
v = Ï€r^2 h = 10 so, h = 10/(Ï€r^2) The surface area is a = 2Ï€r(r+h) = 2Ï€r(r + 10/(Ï€r^2)) = 2Ï€r^2 + 20/r da/dr = 4Ï€ - 20/r^2 = (4Ï€r^2-20)/r^2 da/dr=0 when 4Ï€r^2=20, or r=â&#...
November 1, 2016

geometry
if you mean that the center is (4,-1) and (8,2) lies on the circle, then r^2 = (8-4)^2+(2+1)^2 = 25 so the circle is (x-4)^2 + (y+1)^2 = 25
October 31, 2016

brief calc
a = ∫[4,5] 6x dx = 27 or, since the area is just a trapezoid of height 1, a = (24+30)/2 = 27
October 31, 2016

Algebra
the angles add to 180, so since R=Q+20, Q=R-20 S=Q+115 = (R-20)+115 = R+95 Q+R+S=180 R-20 + R + R+95 = 180 ...
October 31, 2016

Algebra2
Given no choices, I'd just have to say those closest to the turning points...
October 31, 2016

Algebra2
Which points are the best approximation of the relative maximum and minimum of the function? f(x)=x^3+3x^2-9x-8
October 31, 2016

Algebra
2(x + 4x-33) = 104
October 31, 2016

Algebra
add 9, multiply by 5, divide by -2 and change direction
October 31, 2016

Algebra
well, just plug and chug: R(x+h)-R(x) ----------------      h
October 31, 2016

Algebra2
A quadratic equation can be written in vertex form or in standard form. Sometimes one form is more beneficial than the other. Identify which form would be more helpful if you needed to do each task listed below and explain why. a- factor the equation b- graph the parabola c-...
October 31, 2016

Algebra2
y = -x^2+12x-4 = -(x^2-12x)-4 = -(x^2-12x+36)-4+36 = -(x-6)^2 + 32
October 31, 2016

Algebra2
What is the vertex form of the equation? Show steps y=-x^2+12x-4
October 31, 2016

Algebra2
thank you
October 31, 2016

Algebra2
Complex numbers can be graphed on the xy coordinate plane. TRUE OR FALSE My answer is yes
October 31, 2016

Algebra
still can't figure out what you mean by pedro works in 3 days and juan in 4 days does that mean that Pedro works for 3 days, and then Juan works for 4 days? It appears that you are saying it takes Pedro 3 days, and it takes Juan 4 days. Then you ask how long it takes each ...
October 31, 2016

plz sir reiny sir steve sir damon help sor bob
just use the chain rule d/dx arccosh(u) = 1/√(u^2-1) du/dx so, if u = x/√3, that becomes 1/√(x^2/3 - 1) * 1/√3 = 1 / √(x^2-3) since you know that cosh^2(u) = 1+sinh^2(u) d/dx coshu = sinhu, you have y = arccosh(u) coshy = u sinhy y' = 1 y'...
October 31, 2016

math
600 * 1.04^6
October 31, 2016

maths
the slope of AB is -1/4 So, the slope of AC is 4 AB has length √68 = 2√17 So, AC has length √17 = √(1^2+4^2) That means that C = A+(1,4) = (2,9)
October 31, 2016

pre algebra PLZZZ help
what string? and certainly, estimation is often easier than detailed calculation.
October 31, 2016

Pre-Calc/ Trig
4cos^2(2θ-π) = 3 cos^2(2θ-π) = 3/4 since cos(a-b) = cosa cosb + sina sinb, cos(2θ-π) = -cos(2θ) cos^2(2θ) = 3/4 cos(2θ) = ±√3/2 now cos π/6 = √3/2 so, 2θ = π/6, 5π/6, 7π/6, 11π/6 &#...
October 31, 2016

math
facing east, of course.
October 30, 2016

MS.SUE PLEASE HELP!!!
(3/4)(z+8) 6(3x+y) -5(2a+5) in each case, just divide each term by the number you want to factor out.
October 30, 2016

Permutations
11*10*9 = 990 or 11!/(11-3)! = 11!/8!
October 30, 2016

Algebra II
just split up the real and imaginary parts, as usual! 19+42i-21yi+28y = (19+28y) + (42-21y)i
October 30, 2016

calculus
∫√(v^2 sin^2(2π/T t)) dt Looks to me like just ∫|v sin(2π/T t)| dt The absolute value throws in a wrinkle, but the integral is simple enough.
October 30, 2016

Calculus differentiable and continous identify
For continuous, ya got me. Only F looks like it fails. For differentiable, surely F fails, because it isn't even continuous. Also, (a),(b),(d) fail because of the cusps. I am assuming that d(0) is defined somewhere on the y-axis. (f) fails because the ends of the semi-...
October 30, 2016

Physics 11 steve or any physics teacher helpURGENT
The total momentum must be conserved. If the boy slides away to the left, the box must move to the right, since momentum is a vector quantity.
October 30, 2016

algebra 2
If x is the number of years, you need (1 + .038/2)^(2x) = 3000/2000
October 30, 2016

algebra
80 is 4 half-lives, so at t=0, it was 16 (2^4) times as great.
October 30, 2016

Algebra
after x years, the value is 14000 * 0.98^x
October 30, 2016

Calculus AB
#1 f' = (3x+2)e^x since e^x is always positive, just determine where 3x+2 is positive, etc. #2 remember the point-slope form of a line. a) y= x^2 + (e^x)/(x^2 +1) at the point x=3. y' = 2x + (x-1)^2/(x+1)^2 e^x y(3) = 9+e^3/10 y'(3) = 6+e^3/4 So, you want the line ...
October 30, 2016

Math
type in your functions here, and see whether you can see how to arrive at the solutions. http://www.wolframalpha.com/input/?i=%7C(x-3)%2F2%7C
October 30, 2016

math
not sure what you have against a simple minus sign, dividion symbols, etc. The rest of us just use simple ascii characters, such as + - / * < <= > >= all are correct except #8 c+6 < -20 c < -26
October 30, 2016

Pre-Calculus
there are a few standard angles whose exact values we know. By combining them we can get exact values for other angles.
October 30, 2016

Gaussian Elimination Method
http://www.gregthatcher.com/Mathematics/GaussJordan.aspx
October 30, 2016

maths physics
Let the three time periods be x,y,z seconds x+y+z = 20 (5/2 x^2) + (5xy) + (5xz-2z^2) = 20 Now, since it decelerates at 4/5 the rate that it took to accelerate, it will take 5/4 as long to come to rest. So, our third equation is z = 5/4 x Now just solve for the time periods, ...
October 30, 2016

physics
if the angle θ is measured counterclockwise from the +x axis, then the components are x = r cosθ y = r sinθ where r is the magnitude of the directed quantity.
October 30, 2016

maths
think hypotenuse.
October 30, 2016

math
see related questions below
October 30, 2016

math
I suspect a typo. Since they start with the same amount, and the first tank fills more slowly, it will never have more than the second tank.
October 30, 2016

Calculus AB
why the <note>? Just say what f(x) is. You can use the quotient rule if you want, but note that f(x) = (x-6)/(x+6) = 1 - 12/(x+6) so, f'(x) = 12/(x+6)^2 f'(6) = 12/12^2 = 1/12
October 30, 2016

DISCRETE MATH
if a_n depends on previous values of the sequence, then it is recursively defined.
October 30, 2016

math- Set
try using ⊂ for subset (a) ∅ is a subset of all sets. have any thoughts on the others? They really are quite simple.
October 30, 2016

Math 107
just plug your numbers into the formula, which I'm sure you have.
October 30, 2016

maths
x = 4/9 x + (4/9 x + 17) x = 153 girls: 68 boys: 85
October 30, 2016

Math
(10+4)(4+4) - 10*4 (19/16 + 13/4)/(13/4 - 9/16) = 71/43
October 29, 2016

Calculus
geez, why bother? It's a triangle.
October 29, 2016

Calc
you don't give an interval, but let's say it's [1,5]. If you use n rectangles, then the upper approximation will use right sums. (Draw the graph and a few rectangles to see why.) n ∑5/(1+k*4/n) k=1
October 29, 2016

maths
(115+95)km/(1.5+2.5)hr = 210/4 km/hr
October 29, 2016

math
In QIII you have x = -9 y = -1 r = √82 So, now just recall the definitions of the trig functions for a triangle in standard position.
October 29, 2016

math
clearly the first digit is 1 or 2 the cubes are 1 and 8 if 10 is a factor, the number ends in 0 start with that, and see where you get.
October 29, 2016

math
two points on the line or slope and an intercept or a point and the slope or the two intercepts ...
October 29, 2016

Math
since time = distance/speed, 6/(x-3) = 6/x + 1
October 29, 2016

physics
PV = kT, so PV/T is constant. So, you want P such that (P)(120)/(40+273) = (1)(140)/(20+273)
October 29, 2016

Math
use the law of cosines. The angle between the bearings is 35+32 = 67 degrees.
October 29, 2016

math
6*(2(15+31)-5)
October 29, 2016

Calculus
Use as many as you want. That's the n. You can estimate the area with a single rectangle, of width pi/2 and height 1, but it won't be a very good estimate. Also, my bad. I was thinking of sin(x) when I mentioned that the estimate was over- or under-. The reverse for ...
October 29, 2016

Calculus
n ∑(pi/2n)(cos(t*pi/2n) t=1
October 29, 2016

Calculus
It's a good start. Note that since you are using the right-side sum, and cos(x) is concave down and rising on that interval, the sum will be an upper estimate. Use the left-side sum for a lower estimate. Draw a few rectangles and the curve to see why this is true.
October 29, 2016

Math
use the law of cosines.
October 29, 2016

1 MATH QUESTION
the number off coordinates.
October 29, 2016

Math
see related questions below
October 29, 2016

Trigonometry
The angle of depression from the top of a lighthouse across the street is 65 degrees. the angle from the lighthouse to what? And across the street from what? All we know is that the lighthouse is 37 tan28° = 19.67 ft taller than the house.
October 29, 2016

Chemistry
well, velocity = wavelength * frequency
October 29, 2016

Math
well, 1000 years is 2 half-lives, so ...
October 29, 2016

Algebra 2
Assuming that sqrt4(125) means ∜125, then A = 3^(1/2) * 5^(3/4) / 7^3 so, logA = (1/2)log3 + (3/4)log5 - 3log7 The base of the logs does not matter. The rules still hold.
October 29, 2016

math
Recall that for x^2+bx+c the product of the roots is c. If the other root is m, then 4m = k 4+m = 5 Looks like m=1, so k=4 x^2-5x+4 = (x-4)(x-1)
October 29, 2016

Math
just multiply all the numbers by 2.
October 29, 2016

maths
start with 1 and 24 Now start increasing the first and decreasing the second till they ass each other. By then you will have listted all the factors.
October 29, 2016

Math
consider that the amount of sausage never changed. did the solvent remove the fat?
October 29, 2016

Math's
well, how many oranges in 2 dozen?
October 29, 2016

math
1.7/B + 1/B = 1/6
October 29, 2016

Maths
multiply the rows by 3 and 2 and you have 6x-9y = -9 6x-14y = -2 Now subtract to eliminate x, and then y is easy. Use that value of y in either equation to get x.
October 29, 2016

math
must be all 9's, eh?
October 29, 2016

Math probability
well, what is the chance that the 1st sock is blue? Having removed it, what is the chance that the 2nd is blue? The number of blues and the number of socks have both been changed by removing the 1st blue sock. Now just multiply.
October 29, 2016

math
a = F/m, so plug in your numbers.
October 29, 2016

Math Help
It means the number of elements in the set. Clearly you have not studied your material.
October 29, 2016

Math Help
so, do you know what n(a) means? If you do, this cannot be a hard problem.
October 29, 2016

math
ha ha if you can read, just put it into math. If the river's speed is x, then since time = distance/speed, 4/(2+x) = 1/(2-x)
October 29, 2016

math
google is your friend https://www.quora.com/How-do-you-calculate-the-number-of-squares-in-an-n-x-n-square-grid
October 28, 2016

maybe math
If Reiny is right, then to simplify, -1/8 + 1/8^2 = -8/8^2 + 1/8^2 = -7/8^2 or, 2 ∑ -2^k/8^2 k=0 How's that for simple? And all positive exponents!
October 28, 2016

Math Derivative
yes. The good old chain rule. It helps to write them as fractions, so things cancel out: dg/dx = dg/dh * dh/dx I know they usually tell you to avoid thinking of derivatives as fractions, but they really are. It's the same with parametric functions, x(t) and y(t) dy/dx = (...
October 28, 2016

Calculus
a scalar multiple just distributes as in a complex number: a(x+yi) = ax+ayi (1/2)<-3,7> = <(1/2)(-3),(1/2)(7)>
October 28, 2016

Physics
conserve total angular momentum.
October 28, 2016

Calculus
well, y' = -2/(3y), so y" = 2/(3y^2) y' = ...
October 28, 2016

Calculus I
show what you did. This kind of problem always works out that the fencing is divided equally among lengths and widths. So, the entire array will have dimension (50/3) by (50/4) Each pen will be (50/9) by (50/8) Start with 3x+4y = 100 a = xy = x*(100-3x)/4 then find x such that...
October 28, 2016

Math (Confused)
9*10^3 * 9*10^4
October 28, 2016

Math (Finding Vertical Tangent)
looks to me like there is a vertical tangent at x = 2pi/3
October 28, 2016

Algebra
75% is correct. There is a mistake somewhere in the problem or the answer. Could it be that they won 6 and lost 8? That would make the answer 6/14 instead of 6/8.
October 28, 2016

Chem
1 mole occupies 22.4L at STP so, you will have 17.8*22.4L PV = nRT
October 28, 2016

Algebra
cost = revenue to break even So, what is the cost for x pencils?
October 28, 2016

Math
need for what? and how much is a "dash"?
October 28, 2016

Math
if x mL were lost and replaced, then .80(250-x) + .40x = .72*250
October 28, 2016

Math - forget it
Oops - my bad. I misread it. Embershy is correct
October 28, 2016

Math
23/40 - 23/30 = 23(1/40 - 1/30) = 23(3/120 - 4/120) = 23(-1/120) = -23/120 Note above that 23/30 is not 11/15.
October 28, 2016

Math
.30*8 + 1.00x = .35(8+x)
October 28, 2016

Chemistry
The total mass of the solution is x where .0910x = 19.0
October 28, 2016

maths
660 is nowhere close. You want the circumference of a circle. You don't say whether 220 ft is the diameter or the radius, or even the circumference. If the diameter, your new larger circle has diameter 220+6 = 226 If the radius, your new larger circles has diameter 440+6...
October 28, 2016

easy Math
well width * length = area so, ...
October 28, 2016

easy math
(6/2)^2
October 28, 2016

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