Tuesday

December 1, 2015
Total # Posts: 35,894

**Calculus**

Fx = 3x^2 + 2y^3 Fy = 6xy^2 - 9 Fxx = 6x Fxy = 6y^2 = Fyx Fyy = 12x Now just plug in the numbers
*November 17, 2015*

**ipc**

well, v changes by +3.2 m/s every second. So, what is that after 6 seconds?
*November 17, 2015*

**math plz help**

like terms have the same variable. So, ...
*November 17, 2015*

**Trigonometry**

3 = 3 cis0 2+3i = √13 cis x where tan x = 3/2 now divide, and you get 3/√13 cis(0-x) = 3/√13 (cosx - i sinx) = 3/13 (2/√13 - 3/√13 i) = 6/13 - 9/13 i
*November 17, 2015*

**Trigonometry**

b^2 = a^2+c^2-2ac cosB So, plug in your numbers and solve for cos B Then B is cos^-1 of that number.
*November 17, 2015*

**Trigonometry - eh?**

planes fly on headings distant objects have bearings I thought you said the plane flew SW from C to A. Why then do you ask for it? Typo?
*November 17, 2015*

**Calculus**

Partials are easy. Just consider the extra variables as constants. Wx = 4xy-6yz Wy = 2x^2-6xz+10z^2 Wz = -6xy+20yz Now just plug in the numbers.
*November 17, 2015*

**Calculus**

∂R/∂x1 = 700 - 4x1 - 4x2 ∂R/∂x2 = 700 - 4x1 - 4x2
*November 17, 2015*

**math**

since 2 <= f(x) <= 3, and the width of the interval is 6, 2*6 <= ∫f(x) dx <= 3*6
*November 17, 2015*

**math**

oops: y=64
*November 17, 2015*

**math**

4x = 7y x-y = 48 x - 4x/7 = 48 3x = 7*48 x = 7*16 = 112 So, y = 4*16 = 56 check: 112-56 = 48
*November 17, 2015*

**calculus**

If the pen is x by y, then we have xy=720 p = 2x+y = 2x+720/x dp/dx = 2 - 720/x^2 x^2=360 x = 6√10 So, the pen is 6√10 by 12√10 As always, the area is max when the fence is divided equally among lengths and widths. clearly the cost per foot of the fence does ...
*November 17, 2015*

**VERTEX,FOCUS AND DIRECTRIX**

x^2+3y-9 = 0 x^2 = -3(y-3) now use what you know about the parabola x^2 = 4py to discover the properties. In this case, the vertex is at (0,3).
*November 17, 2015*

**Math**

f(x) = x^3(x^2+7) Now you can easily state the zeroes and their multiplicities.
*November 16, 2015*

**math - linear programming**

If there are x boxes of nuts and y boxes of fruit, you want to maximize p=7x+8y subject to 2x+4y <= 1000 2x <= 900 2y <= 400 Now use your favorite linear programming tool.
*November 16, 2015*

**Calc**

v = 1/3 πr^2 h = π/3 (d/2)^2 h = π/12 h^3 dv/dt = π/4 h^2 dh/dt Now just plug in your numbers.
*November 16, 2015*

**Algebra 2**

correct
*November 16, 2015*

**Duplessiss primary**

well, 97 = 6*16 + 1
*November 16, 2015*

**Geometry**

p>p'(-2,-6) for the glide reflection where the translation is (x,y)>(x,y-1) and the line of reflection is x=1. What are the coordinates of P? The answer is (4,-5) I'm looking for the steps of how to get to the answer. 69-year-old grandpa trying to help grandson
*November 16, 2015*

**Algebra**

if each value of y is the same multiple of x, it varies directly. If you can multiply each value of x by some number, k, and get the corresponding value of y, then k is the constant of variation, and y = kx
*November 16, 2015*

**algebra**

Parallel lines have the same slope. So, you want a line with slope = -1 Now you have a point and a slope. Use that to get y+2 = -1(x-2) y+2 = -x+2 y = -x Or, given y = -x-2, you know that any parallel line will be y = -x + b So, plug in x=2 into your equation, and you have y...
*November 16, 2015*

**math**

divide both sides by -13 what do you get?
*November 16, 2015*

**Calculus**

actually, that's a repeated linear. I get 1/(x+2) + 2/(x+2)^2 - (x-2)/(x^2+4)
*November 15, 2015*

**College Algebra**

just put the words into symbols. If the numbers are x,y,z, respectively, then we are told that y=z+5 x=2y x+y+z=87 Now just solve the equations.
*November 15, 2015*

**math**

|6-4| = |6|-|4| = 6-4 = 2 |4-6| ≠ |4|-|6| = 4-6 = -2 -b is the additive inverse of b, so the statement is always true.
*November 15, 2015*

**Quadratic Functions Applications**

#1 -4t-4.9t^2 = -1750 #2 (w+2*3)((w+6)+2*3)-(w)(w+6) = 288 #3 If Mary Beth takes x hours, 1/x + 1/(x+6) = 1/4 #4 clearly a 9x9 square fits the bill Since a square has maximum area for a given perimeter, no other rectangle can do the job.
*November 15, 2015*

**pre calculus**

you gotta use the tan^-1 button on your calculator Or, the 2ndtan or invtan sequence Or go to any online calculator and evaluate arctan(.6524)
*November 15, 2015*

**Trigonometry**

expanding things a bit, we have 4cos^2x - 4sin^2x + 6sinx cosx = 2 2cos^2x + 3sinx cosx - 2sin^2x = 1 (2cosx-sinx)(2sinx+cosx) = 1 Now divide by cos^2x and you have (2-tanx)(2tanx+1) = sec^2x 4tanx - 2tan^2x + 2 - tanx = 1 + tan^2x 3tan^2x - 3tanx - 1 = 0 tanx = (3±&#...
*November 15, 2015*

**Math**

You have the expression. The value can be discovered as below: 8[(20-4)-6] 8[-16-6] 8[-22] -176
*November 15, 2015*

**maths plz help**

1/a + 1/b = 1/3 1/b + 1/c = 1/5 1/a + 1/c = 1/7 add them all up and you get 2/a + 2/b + 2/c = 1/3 + 1/5 + 1/7 = 71/105 1/a + 1/b + 1/c = 71/210 So, it takes 210/71 ≈ 2.95 hours for all three to do the job. That's rather surprising, isn't it?
*November 15, 2015*

**Geometry**

no idea. Where are B and C?
*November 15, 2015*

**math(quadratic equation)**

t+k=30 (t-6)(k-6)=80 (t-6)((30-t)-6) = 80 (t-6)(24-t) = 80 24t-t^2-144+6t = 80 t^2 - 30t + 224 = 0 (t-14)(t-16) = 0 ...
*November 15, 2015*

**math**

The building is 10 times as far away, so it is 10 times as tall as the tree.
*November 15, 2015*

**math**

the larger the divisor, the smaller the quotient. So, as x gets incredibly large, 1/x gets incredibly small. So, as x gets infinitely large, 1/x gets infinitely small, or zero. So, yes, all reciprocal functions have y=0 as their horizontal asymptote. (depending on just what ...
*November 15, 2015*

**math**

a^2+ab-ac-bc = a(a+b)-c(a+b) = (a-c)(a+b) (a^2-c^2)/(a-b) = (a-c)(a+c)/(a-b) Now do the division (multiply by the reciprocal) and the (a-c) factors cancel, leaving (a+b)(a-b)/(a+c) = (a^2-b^2)/(a+c)
*November 15, 2015*

**math**

(p-2q)/(p+2) = 3q p-2q = 3q(p+2) p = 2q+(3p+6)q p = (3p+8)q q = p/(3p+8)
*November 15, 2015*

**math**

(1+.04/4)^(4t) = 5 Now solve for t
*November 15, 2015*

**college algebra**

1/30 + 1/45 = 1/x x = 18 minutes
*November 15, 2015*

**Maths**

Ariel is a person's name An aerial is an antenna recall the definition of tan(x) and you will see that the aerial's height is 200tan58° - 200tan56°
*November 15, 2015*

**College algebra**

in 2h the 1st pipe has filled 1/3 of the pool. 1/6+1/8 = 7/24 That's how much the two pipes together can fill in an hour. So, to fill the remaining 2/3 of the pool takes (2/3)/(7/24) = 16/7 hours
*November 15, 2015*

**Calculus 1**

f = x^2/(x-4)^2 f' = -8x/(x-4)^3 f" = 16(x+2)/(x-4)^4 f is concave up where f" > 0, or x > -2 concave down then, is everywhere else, or x < -2 Unfortunately, there is an asymptote at x=4, so f is concave up on (-2,4)U(4,∞). The graph is concave up ...
*November 15, 2015*

**calc 2**

The curves intersect at π/6, not π/4. The leaves of the rosette return to (0,0) at multiples of π/4, but that's not where the circle intersects the rosette. Using the 8-way symmetry, I'd just integrate over [0,π/6], so a = 8∫[0,π/6] 1/2 (...
*November 15, 2015*

**calc 2**

I'd integrate from -a to a
*November 15, 2015*

**Pre cal**

use the law of cosines. The short diagonal is 7^2+4^2-2*7*4cos55° The longer diagonal lies opposite the supplementary angle, so it is 7^2+4^2+2*7*4cos55°
*November 15, 2015*

**Algebra**

looks good to me
*November 15, 2015*

**Precalculus**

9 ∑ 20-1.5n n=0 9 ∑ 40(-1/4)^n n=0
*November 14, 2015*

**Calculus 1**

f'(t) = -16sin(t) + 16cos(t) f'=0 when sin(t)=cos(t) t = π/4 f(0) = 16 f(π/4) = 16/√2 + 8 = 8(1+√2) > 16 f(π/2) = 0 So, it looks like max = 8(1+√2) min = 0 Let's check the graph: http://www.wolframalpha.com/input/?i=16+cos+t+%2B+...
*November 14, 2015*

**Advanced Functions**

co-sine means sine of co-mplimentary angle. so, cos(90-x) = sin(x) and your function is just -sin(x) Or, you can apply the difference formula, but that is done before the negative -[cos(90-x)] = -[cos90cosx+sin90sinx] = -sinx
*November 14, 2015*

**Math: Word Problem**

well, 450 = 30*15, and 15+30+15=60
*November 14, 2015*

**algebra**

since distance=speed*time, if the boat's speed is x, we have 3(x+6) = 5(x-6)
*November 14, 2015*

**further algebra**

let us assume that the ball is at rest when it bounces less than 1mm. Starting at 30,000 mm, we find that on the 12th bounce it has "stopped" bouncing. So, with r=0.4, and noting that 12 bounces involve a round trip (up and down), we have the sum of a geometric ...
*November 14, 2015*

**Algebra**

if the digits are x and y, the value is 10x+y 10x+y = 3(x+y) 10x+y+45 = 10y+x The number is thus 27 check: 27 = 3*(2+7) 27+45=72
*November 14, 2015*

**Algebra**

#1 Nope. y=2x means that -2 = (-2)(2) Bettr try again. #2 Nope. At least check your guess by plugging in the point. You said -3/2x-1 If (2,-1) is on that line, then (-3/2)(2)-1 = -1 Nope. #3 Nope. x=-3 is a vertical line. A vertical line through (4,2) is not 2x+4, which has a ...
*November 14, 2015*

**Math**

just get out your calculator and divide 1 by 6. What do you get? Or, just type 1/6 in the google search box
*November 14, 2015*

**Rationa Numbers**

8^-2 = 1/8^2 = 1/64
*November 13, 2015*

**Math**

glide: (-3,3) -> (2,3) reflect: (2,3) -> (2,-1) I suspect a typo.
*November 13, 2015*

**Math - Logarithms**

by definition, ln(x) is the power of e you need to get x. Just as log_10(100)=2 because 100=10^2 b^(log_b(N)) = log_b(b^N) = N ln(e^e) = e*ln(e) = e*1 = 1
*November 13, 2015*

**Math - Logarithms**

You could use some parentheses. I'd have done it like this, combining the ln(2x) terms first: 4ln(2x) + ln(6/x) - 2ln(2x) 2ln(2x) + ln(6/x) 2ln2 + 2lnx + ln6 - lnx ln4 + ln6 + lnx ln(24x) Or, doing it kind of your way, 4ln2x + ln(6/x) - 2ln2x ln(16x^4) + ln(6/x) - ln(4x^2...
*November 13, 2015*

**calculus**

so, whatcha got to show us?
*November 13, 2015*

**Calculus**

you can confirm your work here: http://mathworld.wolfram.com/RiemannSum.html
*November 13, 2015*

**Trigonometry**

review the definition of tan(x). Draw a diagram. You will see that the height is 407 tan67° - 407 tan36°
*November 13, 2015*

**Algebra 2**

substitution: x = 13-4y, so 2x+3y = 2(13-4y)+3y = 6 26-8y+3y = 6 -5y = -20 y = 4 so, x=13-4y=13-4*4 = -3 Elimination: Multiply the 1st equation by 2, and you get 2x+8y=26 2x+3y=6 Now subtract and you have 5y=20 and so on as above,
*November 13, 2015*

**algebra 1**

|x|-5 = 7 |x| = 12 So, I'd say (A) You know, your keyboard has || characters...Look right above the \ character which you typed.
*November 13, 2015*

**Al;gebra 1**

assuming a nonzero interior rectangle, 2p < 20
*November 13, 2015*

**math**

if x is positive, so is 1/x. If x is negative, so is 1/x So, the graphs lie in QI and QIII apply that logic to m(x) and n(x)
*November 13, 2015*

**Calculus 1**

or use one of the various online Newton method calculators to verify your work.
*November 13, 2015*

**Calculus 1**

f(x) = x^3+1 - 7/x f'(x) = 3x^2 + 7/x^2 Now let 'er rip
*November 13, 2015*

**Calculus 1**

see related questions below.
*November 13, 2015*

**Physics**

well, just plug in your numbers: F = Gm1m2/r^2
*November 13, 2015*

**@Writeacher**

Dang! I missed a perfect opportunity to post that Latin version.
*November 13, 2015*

**And for my next trick...**

!?
*November 13, 2015*

**Math**

If x were correct, then (40-x) were wrong. Assuming you answered all 40 questions, x/2 - 3(40-x) = 0
*November 13, 2015*

**maths**

-3+(-8) = -3-8 = -11
*November 13, 2015*

**Math**

when the wheel has turned through an angle θ, P is at (x,y)=(cosθ,sinθ). So, since the x-coordinate is at cosθ, Q has moved 1-cosθ left from its starting point. You don't say how fast the wheel is turning, so there's no way for me to know how ...
*November 13, 2015*

**Calculus**

visit http://keisan.casio.com/exec/system/1244946907 and you can use the function f(x) = x^2-27 f'(x) = 2x to approximate √27
*November 13, 2015*

**math**

the inside radius is r=(3 - 5/12) ft So, its volume is πr^2 h Just plug in your numbers. That will give you the volume in ft^3. Then just apply the conversion factor for gal/ft^3.
*November 13, 2015*

**Math**

I has a period of 1/60 seconds. Since it starts at zero, it is a maximum 1/4 period into each cycle, or t=1/240. Then again every 1/60 of a second. It is a minimum at half a period, or 1/120 seconds after each maximum. Just review the properties of the sine function.
*November 13, 2015*

**Math**

play around here to learn how the Z table stuff works: http://davidmlane.com/hyperstat/z_table.html
*November 13, 2015*

**Math**

because 21/28 = 3/4
*November 13, 2015*

**math**

Can't tell without knowing how wide the tiles are, since the border will have 4 corners. If the tiles have width w, then if the pool's width is x, 2(x+20x)+4w = 150
*November 12, 2015*

**World History**

thank you
*November 12, 2015*

**World History**

When do the number of social movements increase? a- During an economic expansion b- during population shrinkage c- during political stability d- when a society experiences a cultural crisis My answer is D
*November 12, 2015*

**Precalc**

15000+9*600 = 20400 At the start of the 10th year, she has had only 9 increases. 10/2 (15000+20400) = 177000 8/2 (2*1500 + 7*300) = 20400 Looks like a small review of A.P.'s is in order.
*November 12, 2015*

**tech math**

The surface area of each cylinder is πdh = π*2.5*4.9 = 38.48 in^2
*November 12, 2015*

**math**

yes, but you are dealing with a square, where a=b. Plug that in and see what you get.
*November 12, 2015*

**Pre-Calculus**

10000 * 0.9^6 On the nth bounce it has to go a round trip, of height 30*(2/3)^n, So we want the 1st 4 terms of a G.P. with a = 30 r = 2/3 30 + 2*S4 = 30+2*30(1 - (2/3)^4)/(1-2/3) = 174.44 ft
*November 12, 2015*

**Math**

If the printed area has width x and height y, xy=382 The area of the poster is a = (x+18)(y+16) = (x+18)(382/x + 16) = 16x + 670 + 6876/x For minimum area, da/dx=0, so 16 - 6876/x^2 = 0 x = 3/2 √191 Now you can figure the poster dimensions.
*November 12, 2015*

**Integral Calculus - Series**

since 1/n^k converges for k>1, and (4n+7)/(3n^3-8n) < (5n)/(3n^3) < 2/n^2 it converges. Note that for sufficiently large n, 4n+7 < 5n. And since 3n^3-8n < 3n^3, a smaller denominator makes for a larger quotient.
*November 12, 2015*

**Algebra HELP!**

graph the two lines. Then see where they intersect. That is the only way to solve using graphs. each line has a slope. What do you mean by "my slope"?
*November 12, 2015*

**Math**

no calculator? 5*10 * 5*10 5*5 * 10*10 25 * 100 2500
*November 12, 2015*

**Science**

wire: a good conductor coating: a good insulator A little study should turn up some examples of each. Or, look at the lamps in your house...
*November 12, 2015*

**Energy science**

a pump is lowered into the hole, and the oil is pushed up. Or, a pipe inside another pipe is pushed down, and air or water is pumped down the outside, and oil is thus pushed up the inside. Or, google pumping oil from deep wells.
*November 12, 2015*

**science**

kitten boots, obviously.
*November 12, 2015*

**Science**

Power = Amps * Volts
*November 12, 2015*

**algebra**

a+d = -6 a+4d = 48 so, 3d=54 d=18 so, a=-24 and the sequence is -24 -6 12 30 48 ...
*November 12, 2015*

**Maths**

It's already factored! You need to review how to multiply polynomials It all hinges on the distributive property. (x+1)(x-3) = x(x-3)+1(x-3) = x^2-3x + x-3 = x^2-2x-3 Now multiply that by (x-4) and you have (x^2-2x-3)(x-4) = x^2(x-4)-2x(x-4)-3(x-4) = x^3-4x^2-2x^2+8x-3x+12...
*November 12, 2015*

**Algebra Probability PLEASE HELP**

oops. my bad. That would be 1/4 and 3/4, not 1/5 and 4/5
*November 12, 2015*

**Algebra Probability PLEASE HELP**

As you know, the probability of answering k out of n questions correctly, given P(correct) = p, is nCk * p^k * (1-p)^(n-k) So, since you have n=5 k=3 p=1/5 p(3 of 5) is 5C3 * (1/5)^3 * (4/5)^2 = 32/625 That is the theoretical probability. For experimental, you'd need to ...
*November 12, 2015*

**Probability**

No idea. Take the test a few times and see how many of those times you get 3/5 correct.
*November 12, 2015*

**ALGEBRA**

well, if 9 is one factor of 36, the other is 4. So, since you have +5x, you need (x+9)(x-4)
*November 12, 2015*