Saturday

July 4, 2015

July 4, 2015

Total # Posts: 21,421

**Calculus**

You already did it. f(0) = 0 f(pi) = 1 etc, at the four points where the derivative is zero
*June 15, 2015*

**Calculus**

You mean cos x sin x = 0 when cos x = 0 or when sin x = 0 when cos x = 0, then sin x = 1 and you have a max when sin x = 0, then cos x = 1 and you have a min
*June 15, 2015*

**Calculus**

LOL, |sin x| is always </= 1 it is at + pi/2 and 3 pi/2 where cos x , the derivative of sin x, is 0
*June 15, 2015*

**physics**

I also get -0.0391
*June 14, 2015*

**physics**

I am not going to answer the others because they are really the same as this one. For example if you have charges 2q and - 2q within a closed surface, the net E flux out is zero.
*June 14, 2015*

**physics**

The Gauss' Law flux = integral E dot dA = Q/epsilon The Gauss law states that electric net flux through any Gauss surface is directly proportional to the net charge enclosed by the surface where is permittivity of vacuum
*June 14, 2015*

**physics**

Huh ?? Gauss! Does not matter shape or size of surrounding surface. Flux out proportional to charge inside.
*June 14, 2015*

**physics**

if you have Q per square meter (maybe call it sigma) net flux out of the square meter is Q/epsilon Looking at both sides of the sheet we have surface area of the enclosure = 2 square meters flux = E * 2 m^2 = Q/epsilon
*June 14, 2015*

**Algebra2**

2(3x-5)= 16 6x -10 = 16 6 x = 26 x = 13/3 and 2(-3x+5) =16 -6x + 10 = 16 6 x = -6 x = -1
*June 14, 2015*

**geometry**

meters, seconds, g = 9.8 m/s^2 h = Vi t - 4.9 t^2 tan q = h/x so x tan q = Vi t - 4.9 t^2 observe angle q at time t solve for x at time t or if Vi is the unknown solve for Vi at x and t then solve for h
*June 14, 2015*

**Calculus**

I have no idea where Q is
*June 13, 2015*

**Calculus**

4 s + 2w + 4w = 4 s + 6 w = 17 A = s^2 + w(2w) = s^2 + 2 w^2 s = (17-6w)/4 A = (1/16)(17-6w)^2 + 2 w^2 dA/dw = 0 at min 0 = (1/8)(17-6w)(-6) = 4 w (3/4)(17-6w) = 4 w 3 (17-6w) = 16 w 51 - 18 w = 16 w 34 w = 51 w = 51/34 = 1.5 then find s and w and 2 w
*June 13, 2015*

**Pre-Calculus**

we want (x-h)^2/a^2 +(y-k)^2/b^2 = 1 now x-h = a cos t so (x-h)^2 = a^2cos^2 t so (x-h)^2/a^2 = cos^2 t similarly (y-k)^2/b^2 = sin^2 t so (x-h)^2/a^2 + (y-k)^2/b^2 = cos^2 + sin^2 = 1
*June 13, 2015*

**typo**

but we know t = 19.5/x should be t = x/19.5 of course
*June 12, 2015*

**Physics**

Horizontal, no force, u =constant so x = 19.5 t so t = x/19.5 Vertical, f = -9.81 m/s^2 * mass = m a so a = acceleration = - 9.81 so a = -9.81 v = Vi - 9.81 t v = 15.4 - 9.81 t then y = initial height + 15.4 t - 4.9 t^2 call initial height of quarterback hand Hi y = Hi + 15.4 ...
*June 12, 2015*

**Physics**

I do not care if she is thin or fat. falls 9 meters, how long? h= (1/2) g t^2 18 = 9.8 t^2 t = 1.36 falling goes 1.75 meters horizontal in 1.36 seconds 1.75 = u t = u (1.36) u = 1.29 m/s horizontal speed
*June 12, 2015*

**Physics**

This is not Physics. tourist runs distance d bear runs distance (d+31.1) same time t d = 3.24 t d+31.1 = 4.5 t so d + 31.1 = 4.5(d/3.24) 3.24 d + 100.7 = 4.5 d d = 80 meters max this tourist is no track star :(
*June 12, 2015*

**Alg 2 HELP!**

-5, 1 , 2 http://www.wolframalpha.com/widgets/view.jsp?id=a7d8ae4569120b5bec12e7b6e9648b86 (right away you should see that one works, then you have a quadratic) domain of parabola is all real x. (range is another story) g = (2x+1)^2 + 3(2x+1) now you multiply out and collect ...
*June 12, 2015*

**alg 2**

Yes it is (x+4)(x^2+9) x = -4 you know however x^2+9 = 0 x^2 = -9 is x = +3i or x = -3i (not rational real)
*June 12, 2015*

**Alg**

http://www.mathportal.org/calculators/polynomials-solvers/polynomial-graphing-calculator.php
*June 12, 2015*

**math**

4 is not it I think but 3 kind of looks reasonable
*June 11, 2015*

**math**

in this system of units, remembered only by ancient mathematicians, g = 32 ft/s^2 approximately. so a = - 32 v = Vi - 32 t = 38 - 32 t h = Hi + Vi t + (1/2) a t^2 0 = 30 + 38 t - 16 t^2 or 16 t^2 - 38 t - 30 = 0 8 t^2 -19 t -15 = 0 solve that quadratic for t, use the positive ...
*June 11, 2015*

**geometry**

think square 3 meters on each side area = 3*3 = 9 then square 6 meters on a side, double area = 6*6 = 36 or four times length ratios = 2 area ratios = 4 2^2 = 4
*June 11, 2015*

**geometry**

areas scale as square of length ratio so 5/2 in area ---> sqrt(5)/sqrt(2) in length so 25 * sqrt 2/sqrt 5 = 15.813883
*June 11, 2015*

**Bayes' Theorem**

say 100 students 40 from Ka .04*40 = 1.6 fails 50 from Ill .02 * 50 = 1 fails 10 from Oh .06 * 10 = .6 fails total failures = 1.6+1+.6 = 3.2 That is 3.2/100 = 3.2 % = .032 3.2 fail, 1.6 of whom are from Ka 1.6/3.2 = .5 or 50% BUT you said use Bayes so P(Ka if failed) =P(failed...
*June 11, 2015*

**physics**

melting ?
*June 10, 2015*

**Math117A**

height/shadow = 4.2/12.6 = 20.4 /x 4.2 x = 12.6 * 20.4 x = 12.6 * 20.4 / 4.2 x = 61.2 check, the shadow should be about three times as long as the object is high in this problem. It is.
*June 10, 2015*

**algebra2**

3 x - 10 x - 20 = 13 - 7 x - 7 x = 33 - 7x 0 = 33 no solution please try these and post your attempt. I am getting bored.
*June 10, 2015*

**algebra2**

x = -22 You can solve that :) Now Karla, try the problem before posting it.
*June 10, 2015*

**algebra2**

10 x + 30 = 10 x + 30 ANY value of x works INFINITE number of solutions BUT what if it were 10 x + 30 = 10 x + 40 then there would be no solutions at all
*June 10, 2015*

**Finite Math**

You are welcome :)
*June 10, 2015*

**Finite Math**

100 students 50 had pre calc - 15 got A, 35 not A 50 no pre cacl - 10 got A, 40 not A sure looks like 35 of the hundred :)
*June 10, 2015*

**algebra2**

2 x = 145 so x = 145/2 the end
*June 10, 2015*

**chemistry**

by the way http://www.quora.com/How-much-water-can-you-split-into-hydrogen-and-oxygen-using-electrolysis-with-one-kilowatt-hour-of-electricity
*June 10, 2015*

**chemistry**

3 hours * 3600 seconds/hour = 10800 seconds 10800 seconds * 0.1 amps = 1080 Coulombs H2O --> 2H+ + O-- 1 mol electrons = 96,500 Coulombs so 1080 C * 1/96500 = .0112 mol electrons looking at equation, we need 2 mol electrons for every mol of H2 so we get .0056 mol of H2 ....
*June 10, 2015*

**science**

Draw a sketch diagram 2 * 5 cos 30 = 8.66 m/s at 30 degrees to each
*June 10, 2015*

**Chemistry**

Ni is about 68.7 grams per mol. so 138/68.7 = 2.008 mol of Ni that is 2.008 mol * 6.02*10^23 atoms/mol = 12.1 *10^23 atoms (quite a few )
*June 10, 2015*

**Chemistry**

by the way iron is also about 8 times as dense as water (1 g/cc or 1000 kg/m^3) and aluminium is less and concrete is about half. That gives you a bit of a check.
*June 10, 2015*

**Chemistry**

That looks right to me.
*June 10, 2015*

**Math**

Iris, You had your choice of 6% compounded or 13% simple for four years. 13% simple wins.
*June 10, 2015*

**Math**

when you compound at interest rate x percent every period you multiply by (1+x/100) so for 4 years at 6% multiply four times by (1 + .06) which is the same as multiply by 1.06^4 if it were 6% per year compounded monthly thet would be 6%/12 per month .06/12 = .005 so we would ...
*June 10, 2015*

**Math**

Well how did you do it really ?
*June 10, 2015*

**Math**

13% is so much more than 6% that the compounding will not catch up for many years.
*June 10, 2015*

**Math**

1.06^4 = 1.26248 *2000 = 2524.95 so earned 524.95 0.13 * 4 =.52 .52 * 2000 = 1040 so earned 1040.00 go with the 13 % simple
*June 10, 2015*

**Chemistry**

how many Joules do you need? Joules needed = specific heat * mass * change in temp then watts * seconds = Joules needed
*June 9, 2015*

**Chemistry**

C * m (60-40) = C * 50 (40-20) so m = 50 grams or .050 Kg
*June 9, 2015*

**History**

Should I laugh or cry?
*June 9, 2015*

**Calc 1**

sure looks like it to me
*June 9, 2015*

**Calc 1**

Hey, you can google too :)
*June 9, 2015*

**Calc 1**

not necessarily http://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=9&cad=rja&uact=8&ved=0CEgQFjAI&url=http%3A%2F%2Fwww.mathsisfun.com%2Fcalculus%2Fdifferentiable.html&ei=2wt3VbzLIMGasQXEoIEI&usg=AFQjCNG-Oqx8EjGrCBl7-c8WA0YYFZ28ag&sig2=WquSfxU_It3cBOBGKCGExg&bvm=bv....
*June 9, 2015*

**Calc 1**

True, if more then not a function http://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=3&cad=rja&uact=8&ved=0CDMQFjAC&url=http%3A%2F%2Fwww.milefoot.com%2Fmath%2Fcalculus%2Flimits%2FFindingAsymptotes12.htm&ei=ZAt3Ve-jC4mQsAXlt4HgDQ&usg=AFQjCNHZjboUch1fdELGYXBuIZC-Tnu_rg...
*June 9, 2015*

**Calculus 1**

well, if x = .99 I get 1.50 if x = .999 then 1.500 that is because numerator = (x-1)(x+2) denominator = (x-1)(x+1) so what we really have is (x+2)/(x+1) which is 1.5 at x = 1 It is true that the original function is undefined at x = 1
*June 9, 2015*

**physics**

They are brakes. after 5 sec at constant v Vi = 20 v = 20 + a t where t is total time - 5 v = 0 when t = 8 so 0 = 20 + a (8) a = -20/8 = - 5/2 so v = 20 - (5/2) t = 20 - (5/2)(time - 5)
*June 9, 2015*

**Math**

11 with vanilla + 11 with chocolate = 22 , right
*June 9, 2015*

**Calc 1**

y at x = 5 = a then y^2 = 25 all right when x = 5
*June 9, 2015*

**math**

total N = 330 + 900 = 1230 Total E = 640 + 370 = 1010 so sqrt (1230^2 + 1010^2)
*June 9, 2015*

**Calc 1**

nope, what if y = L (x-a)/|x-a|
*June 9, 2015*

**Math**

pi is actually about 22/7 This problem is a lot harder than it looks because you should really pack the discs in a hexagonal pattern but I suspect the best we can do is put squares around the circles. 100 /14 = 7.14 so 7 lengthwise 60/14 = 4.28 so 4 that direction 7 * 4 = 28 ...
*June 9, 2015*

**math trigonometry**

I have no reason to believe it is true.
*June 9, 2015*

**SCIENCE**

A to B speed = 300m/170 seconds velocity = speed if that direction is + then A to C distance = 300 + 100 = 400 average speed = 400/230 but total displacement = +300 - 100 = 200 so'=average velocity = 200/230
*June 9, 2015*

**math**

I do not think so. Sketch a graph.
*June 8, 2015*

**Physics**

x = 1.40 t^2 - .0505 t^3 at t = 0, x = 0 at t = 1.91, x =1.40 * 1.91^2 - .0505 * 1.91^3 = 4.755 meters so 4.755 meters in 1.91 seconds = 2.5 m/s do the others the same way, find out how far it went in the time interval and divide by the time interval
*June 8, 2015*

**statistics**

5/15 * 4/14
*June 8, 2015*

**MATH**

x/10 = 37/8 so x = 370/8 (370/8)/16 = 370/128 = 2 114/128 = 2 57/64
*June 8, 2015*

**math**

2* (1/2) pi (1) + 2*3 maybe ?
*June 8, 2015*

**Math help please.**

7 yes 8 A because -3 * -2 = +6
*June 8, 2015*

**Math help please.**

6)-2r(8r+5) A)-16r^2+5 B)-16r+10 C)-16r-10r** D)-16r-10 Nah, -16 r^2 - 10 r probably c but a typo
*June 8, 2015*

**Math help please.**

7^4/7^2 = 7^2 = 7*7 = 49 right
*June 8, 2015*

**Math help please.**

4) 50 A)0 B)5 C)1 D)-5 Perhaps you mean 5^0 but anything^0 = 1
*June 8, 2015*

**Math help please.**

3) 4^4/4^6 4 - 6 = -2 4^-2 = 1/4^2 = 1/16 A)-16 B)16 C)1/16 D)-1/16
*June 8, 2015*

**Math help please.**

2) h^14/h^5 14 - 5 = 9, not 19
*June 8, 2015*

**Math help please.**

1) x^9/x^2 = x(9-2) = x^7
*June 8, 2015*

**maths**

if the second hand moves 180 degrees, that is half a minute .5 min (360 degrees/60 min) = 3 degrees
*June 8, 2015*

**Calculus**

Oh, go with what Steve said.
*June 8, 2015*

**Calculus**

profit = p(x) - C(x) = 50-.01 x - 10 - 2x = 40-2.01 x max at x = 0 I bet you have a typo though.
*June 8, 2015*

**math**

well one way is a parabola write a parabola that goes through (4,1) (6,1.5) and (8,6) first (4,3) (6,0) and (8,0) Y1 = 3(x-6)(x-8) /(4-6)(4-8) = 3(x^2 -14 x + 48)/ 8 second (4,0)(6,1.5)(8,0) Y2 = 1.5 (x-4)(x-8)/(6-4)(6-8) = -(1.5 x^2 -18 x +48)/4 third Y3 = 6(x-4)(x-6)/(8-4)(8...
*June 7, 2015*

**math**

whoops, I dd it for 300 of fence, not 200
*June 7, 2015*

**math**

if two internal petitions the 4 x needed for cross fencing + 2 L needed for length P = 4 x + 2 L =300 or L = 150 - 2 x A = x L = x (150 - 2 x) = 150 x - 2 x^2 if you know calculus: dA/dx = 0 at max = 150 - 4 x so x = 150/4 = 37.5 then L = 150 -2*37.5 = 75 AREA = 37.5*75 = 2812...
*June 7, 2015*

**COLLEGE MATH**

I do not know what level of math you are at. If calculus then dC/dx = 0 at min = .4 x =96 so x = 240 If Algebra 2 level then complete the square to find vertex .2 x^2 - 96 x = -12095 x^2 - 480 x + 240^2 = - 60475 x^2 - 480 x + 240^2 = - 2875 (x-240)^2 = -2875 so x = 240 and C...
*June 7, 2015*

**Another math related question**

4/10 * 7/15 = 14/75
*June 7, 2015*

**Calculus**

you have P = 2 x + 154/x BUT you took the derivative incorrectly P' = 2 -154/x^2 so for min or max 0 = 2 - 154/x^2 or x^2 = 77 NOTE d/dx (1/x) = -1/x^2
*June 7, 2015*

**physics**

any acceleration is down the slope, perpendicular to the force we are interested in. That normal force is the component of weight normal to the hill surface which is m g cos 25
*June 7, 2015*

**physics**

If two capacitors are in parallel, they hold more charge for a given voltage. We know that C = Q/V here C1 = Q1/V C2 = C2/V C1 + C2 = (Q1+Q2)/V so final C = C1 + C2 In other words, if in parallel, add capacitances because you add charges per unit voltage
*June 7, 2015*

**to damon**

You are welcome - good luck !
*June 7, 2015*

**algebra**

ah ham you know Pascal's triangle so you know binomial theorem after all now call a = 4 y call b = x then (a+b)^4 = a^4 + 4 a^3b + 6 a^2b^2 + 4 a b^3 + b^4 which is 256 y^4 + 256x +6 (4y)^2 x^2 etc
*June 7, 2015*

**maths**

sin PQR = 300/600 = 1/2 so PQR = 30 degrees that is 30 degrees south of west or 60 degrees west of south which id a compass bearing of 180 + 60 = 240 degrees clockwise from north cos 30 = RQ/600 RQ = 520 m
*June 7, 2015*

**algebra**

no imagine (x-y)^2 it is not x^2 - y^2 but x^2 - 2 x y + y^2 You need the "binomial theorem" If you have learned it your problem is straightforward, follow the recipe. If you have not had it in your course, I feel for you because you will have to do it step by ...
*June 7, 2015*

**algebra**

(x^4 y^5)^5 = (x^4)^5 (y^5)^5 = x^20 y^25
*June 6, 2015*

**Physics**

do the fall first v = g t 44 = 9.81 t t = 4.49 seconds falling now the up part Vi = 24.4 v = Vi - g t 0 = 24.4 - 9.81 t where t is time rising t = 2.49 seconds upward so 4.49 + 2.49 seconds
*June 6, 2015*

**Physics**

Yes, your wording indicates that you need help. You not only have to heat the water to 100 deg C You have to BOIL IT as well ! so look up the specific heat of water, call it C then LOOK UP THE HEAT OF VAPORIZATION of water. then heat in = 2 * specifc heat * (100-37) + 2 * heat...
*June 5, 2015*

**6th Grade Probability**

1/4 of the times you play (1/4)36 = 9
*June 5, 2015*

**Physics**

wavelength = twice string length to get node at each end and bulge in middle. L = (1/2) wavelength wavelength = speed * period = speed/frequency so L = (1/2) v/f
*June 4, 2015*

**Algebra**

check below http://www.jiskha.com/display.cgi?id=1433381900
*June 4, 2015*

**Physics**

You are welcome.
*June 4, 2015*

**Physics**

The tension and mass density determine the speed of the wave along the string. The input frequency is the wave frequency wavelength = speed * period = speed/frequency so frequency, tension and mass density right
*June 4, 2015*

**Physics**

A yes B yes C No D yes I agree.
*June 4, 2015*

**Algebra**

L^2 + w^2 = d^2 (d-3)^2 + (d-8)^2 = d^2 d^2 - 6 d + 9 + d^2 -16 d + 64 = d^2 d^2 - 22 d + 73 = 0 d = [ 22 +/- sqrt(484 - 292) ] / 2 d = [ 22 +/- 13.9 ] / 2 d = 17.9 or 8.1 8.1 is impossible if the area is 84 so d = 17.9 ------------------- check then w = about 10 and L = about...
*June 4, 2015*

**Math**

66 = 2*33 = 2 * 3 * 11 99 = 3 * 33 = 3 * 3 * 11 20 = 2*10 = 2 * 2 * 5 etc, boring
*June 4, 2015*

**Math**

look at b^2 - 4 a c if +, then two intercepts if 0, then just grazes the x axis, one intercept if -, then never hits the axis, imaginary roots only if a x^2 + b x + c = 0 then - (a x^2 + b x + c) = 0 is the same because +0 = -0
*June 4, 2015*

**math**

sin^4x-cos^4x = (sin^2 x+cos^2 x)(sin^2 x -cos^2 x = 1 (sin^2 x - cos^2 x) = 2 sin^2 x - 1
*June 4, 2015*