# Posts by Damon

Total # Posts: 29,993

**calculus!**

at x+h y = 1/(3-x-h) at x y = 1/(3-x) subtract 1/(3-x-h) -1/(3-x) [(3-x) -(3-x-h)]/[(3-x-h)(3-x)] [ h]/[ x^2-6x+xh-3h+9] divide by h 1/[x^2-6x+9 +xh-3h] let h --->0 1/(x-3)^2

**Math - Coordinate Geometry**

3y = 2 x + 3 is y = (2/3)x + 1 slope = 2/3 so y = (2/3)x + b if parallel -4 = (2/3)6 + b b = -8 so y = (2/3)x-8 3 y = 2 x - 24

**math**

3078+582 = 3660 =3*1000 + 0*100 + 7*10 +8*1 +0*1000 + 5*100 + 8*10 +2*1 =3*1000 + 5*100 +15*10 +10*1 =3*1000 + 6*100 + 5*10 +10*1 =3*1000 + 6*100 + 6*10 + 0*1 = 3660

**Geometry**

I guess it is supposed to be a triangle? If so ac can not be longer than 11+13 = 24 and it can not be shorter than 13-11 = 2 DRAW IT !

**Sociology**

They mean the same thing to me. Homogeneous is opposite to diverse.

**calculus**

LOL, either way I do physics, I find t easier to visualize step by step.

**calculus**

dV/dt = 3ft^3/min(1 min/60s) = .05 ft^3/s so V = .05 * 30 = 1.5 ft^3 at 30 s V = (4/3) pi r^3 so r = 0.71 ft at 30 s dV/dr = 4 pi r^2 (the surface area of course) but dV/dt = dV/dr * dr/dt so dr/dt = dV/dt / (4 pi r^2) dr/dt = .05 /(4 pi*.71^2) = .00789 feet/second

**Gauss-Jordan elimination**

-3 +3 -21 +3 +2 -4 ============= http://www.idomaths.com/gauss_jordan.php ===================== 1 0 2 0 1 -5 x= 2, y = -5

**HELP SCIENCE**

Which do you think? What does north and south pole mean?

**augmented matrix**

No unique solution, equations are the same +3 +1 -11 -9 -3 +33 http://www.idomaths.com/gauss_jordan.php 1 0 -3.667 0 0 0 x = -3.6666.... or -11/3 y can be anything equation 2 is -3 times equation 1 Therefore the two lines are the same, they do not intersect, there is no solution

**Physics**

3.) An 80.kg climber with a 20.0 kg pack climbs 8848 m to the t?op of mount everest. how much work did the climber exert in the climbing the mountain ==================== 100 kg up 8848 meters 100 * 9.81 * 8848 = 8,679,888 Joules (That is the useful work, his efficiency would ...

**Physics**

When the string is cut, the bob has only horizontal velocity u. It keeps that horizontal velocity u until it hits the ground because there is no horizontal force after that. So there are two separate problems here: 1. How far does it go at constant speed u for time t? 2. If ...

**Math 4th Grade**

You are welcome, good luck.

**Math 4th Grade**

280 = 2 x m 28 = 2 x 14 280 = 2 x 140 so m = 140 I am not sure why I would want to do it that way though. If you can handle 2 x 14 I bet you could handle the tens part.

**Sets**

Union is 107 Intersection is 13 draw Venn diagram 69 + A alone = 107 so A alone = 38 plus A and B = 38+13 = 51

**Measurement/math**

35*circumference = 100

**Algebra**

check it yourself like this: 11 + (-.7) = -15(y) ????? I think x = 19 and y = -2 http://www.idomaths.com/gauss_jordan.php with +1 15 -11 +2 -5 +48

**Math**

1/4 + what = 11/12 ???? 3/12 + what = 11/12 well how about 8/12 so 1/4 + 8/12 = 11/12 or 1/4 + 2/3 = 11/12

**Algebra II**

What is an L ?? Perhaps a Newton??? if cm^2/then D for Dyne anyway v = k/p 16 cm^3 = k / 20L/cm^2 k = 16*20 v = 16*20/2.2 = 145 cm^3

**maths calculas part**

144/4 = 36 36*36 = 1296 m^2 now how did I know it was square? 2x+2y = p = perimeter so x+y = p/2 so y = p/2-x A = x y = x(p/2-x) A = (p/2)x - x^2 or x^2 - (p/2)x = - A x^2 -(p/2)x + (p/4)^2 = -A + p^2/16 [ x - (p/4)]^2 = - (A-p^2/16) so vertex at area = (p/4)^2 and x = y = p/4...

**Maths**

if there are five of them and the median is five I think five is an integer a b c d e c = 5 (a+b+c+d +e)/5 = 5 so a+b+5+d+e = 25 a+b+d+e=20 with d and e >5 and a and b <5 well what if a = 1 b= 2 d= 7 e = 10 1 2 5 7 10

**precalculus**

P(k+1) = p(k) + 5

**Math**

volume is proportional to length cubed for similar geometry 2 times length is 4 times area 2 times length is 8 times volume so 1875(16/40)^3 = 1875(.064) = 120cm^3

**physics**

centripetal acceleration: To stay at the same radius, a water particle of mass m must have a force on it inward of m v^2/r. Until it hits the walls of the container, that force is missing. If the water particle happens to hit upon a hole in the wall or dribbles down the wall, ...

**Science 6**

B skunk eats toads I do not think toads and mice compete for who has the honor of being eaten by the fox

**Algebra**

1 q + 1 n = 13 1 q + .2n = 8.2 ---------------subtract .8 n = 4.8 so 6 nickels

**precalculus**

as you can see in the other answers, yes 4y^2+8y-2

**precalculus**

I guess you might mean: x = t^2-6 y = .5t - 1 ????? if so, just substitute 2y = t -2 t = 2 y +2 then x = 4(y^2+2y+1) -6 x = 4y^2 + 8y - 2 sketch that parabola

**precalculus**

hyperbola opening right and left center at (0,0) crosses x axis at -1 and +1 slopes at corners = +/- 2

**linear programming**

maximize p p = 6s+5b s+b</=70 b>/=20 s>/=10 sketch a graph there are two intersections to check (s,b) = (10,60) here p= 60+300 = 360 and (s,b) = (50 ,20) here p=300 + 100 = 400 (winner)

**physics**

Fup = 400 Fdown = 9.81*50 =491 so accelerating down a down = 91/50 m/s^2

**Science-y Math-y Stuff**

0.8 x = 4,000

**Science**

There was this guy in Sicily , Archimedes: http://www.math.nyu.edu/~crorres/Archimedes/Lever/LeverIntro.html http://en.wikipedia.org/wiki/Lever

**Physics**

alternatively you can use conservation of energy kinetic energy at bottom = potenial energy at top (1/2)mVi^2 = m g h so Vi^2 = (2 g h) h = Vi^2/2g

**Physics**

get vetical component of velocity up at ground, call it Vi. If shot at angle A up from horizontal then Vi = V sin A during flight acceleration = -g or 9.8 m/s^2 down or 32 ft/s^2 down speed up = v = Vi - g t = Vi -9.8 t or = Vi -32 t at top, v = 0 so t = Vi/9.8 or t = Vi/32 ...

**Physics**

average speed during initial slowdown = (80+40)/2 = 60km/h 60 km/h * t = 0.5 km t = 5/600 hours = (1/120)hr (1 hr/120)(60min/hr)(60s/min) = 30 seconds so a = change in speed/time = -40 km/hr /30 s = (-40 * 1000 m/3600s)/30s = -(4/3)/3.6 m/s^2 so Vi = (40/3.6) m/s final v = 0 =...

**I THINK I FIGURED IT OUT!**

8 works if you reverse order

**Math**

2/5 = 10/x x = 25

**Pre-Calculus**

well if you mean (x^2-1) it is D but if you really mean (lim x^2) -1 which is what you typed it is A

**Algebra**

9(r-2)<-73 or 9(-r+2)<-73 first one: 9 r -18 < -73 9 r < -55 r < -55/9 sure looks like a solution second one: -9 r + 18 <-73 9 r -18 > 73 9 r > 91 r >91/9 so second solution

**pre-calculus**

square :) side = 50/4 = 25/2 A = x y P = 2x+2y = 50 so y = (25-x) A = x(25-x) = 25 x - x^2 x^2 -25 x = -A x^2 - 25 x + (25/2)^2 = -A + 625/4 x = 25/2 sure enough so y = 25/2 and A = 625/4 = (25/2)^2

**Algebra**

1. 8 is a factor of 12?? 12/8 = 3/2 = 1.5 2 55/5 = 11 3. You said what P was 4 and 5 are incomplete problem statements both A and B are subsets of U 2 is the intersection of A and B

**physics**

suspect 1000 kg not 100 kg but anyway gravity down = 9.81 *100 = 981 N acceleration down = v^2/r Up force = F so 981 - F = ma = 100 v^2/r so F = 981 - 100 (400)/200 = 781 N but as you know if it is a real car I think 7810 N

**Physics**

I will guess that you mean the current leaves the battery and runs through r2 then splits and runs through r1 and r3 in parallel then joins again and runs through r4 back to the battery. If I guess right then r1 and r =3 in parallel are r1 r3 /(r1+r3) = 90*40/(130) = 3600/130...

**SS HEEELLLPP!!!**

I think that is a matter of opinion, not history. Check your text for what they say. I am not sure the Great Wall was such a success militarily. There seem to have been plenty of intruders from the north after. My own opinion is that the most important thing was the ability of...

**Physics**

x momentum = 16*30 = 480 g cm/s -x momentum = 4*50 = -200 g cm/s total x momentum = +280 g cm/s That will NOT CHANGE ! new mass = 16 + 4 = 20 g so 20 * Vx = 280 Vx = 14 cm/s

**8TH GRADE MATH**

60 sqrt 2 hypotenuse = sqrt (60^2+60^2) = sqrt (2 * 60^2) = 60 sqrt 2 = 84.85

**physics**

Vi = 30 sin 30 = 15 = initial speed UP u = 30 cos 30 = 26 = horizontal speed until caught v = Vi - 9.81 t at top v = 0 (First answer) so at top t = 15/9.81 = 1.53 seconds upward bound THE ACCELERATION IS -9.81 m/s^2 the ENTIRE TIME that it is airborne

**check for typo**

The way you wrote it k x^2 = (3k-5) x = +/- sqrt(3 - 5/k) but I wonder if you mean kx^2 -3kx+5 which would be x = [3k +/- sqrt(9k^2-20k) ]/2k

**Chemistry**

k m/r^2 so (3/4)(804)

**algebra**

I guess maybe you mean 6/ (?3 + 2 ) if so then [ 6/(?3+2)] * [(?3-2)/(?3-2)] 6(?3-2)/[3-4] -6?3 + 12 which is B

**Physics**

Archimedes said Force up = weight of fluid displaced. It displaced 6.4-5.6 = 0.8 kg of water so its volume is V = .8 kg (m^3/1000kg) = 8*10^-4 m^3 so its density is (6.4 /8)10^4 kg/m^3 =8000 kg/m^3 might be iron

**physics**

suspect STATIC is 0.68 .68 m g = starting Force .55 m g = constant velocity Force

**Algebra**

1-4k >= -11 and -1+4k >=-11 -4k >= -12 _and ___4k>=-10 4 k <= 12 __and_____k>=-2.5 k <= 3 note arrow reverse when signs changed so in the end between -3and +3 -2.5 <= k <= 3

**Physics**

You could have done that, patience :)

**Physics**

Total force up =100(9.81) = T1 sin37 + T2 sin 53 Total horizontal force = 0 = T1 cos 37 - T2 cos 53 use that to get T1 and T2 now for example moments about left end T2 sin 53 *5 = 100*9.81* X

**Math**

3(-2)(-2) -2(-2)(3) + 10 12 + 12 + 10 34

**system of equations**

Oh, and you might want to click on "very detailed solution" :)

**system of equations**

Click on Gauss Jordan there of course.

**system of equations**

5 -3 -34 10 -5 -65 (-5, +3) see http://matrix.reshish.com/gaussSolution.php

**whoops sorry**

xp = 100 +/- 50sqrt2 so about 30 (NOT 70 AS I SAID) if xp = 30 yp = .01x^2 = 9

**Calculus**

y = a x^2 100 = a(10,000) a = .01 so our parabola is y = .01 x^2 now a tangent to that parabola must pass through (100,50) slope = .02 xp at parabola y = (.02xp)x + b 50 = 2 xp + b b = 50-2xp but yp = .01 xp^2 and yp =.02xp^2 +50-2xp .01 xp^2 = .02xp^2 + 50 - 2 xp .01 xp^2 -...

**where is the equation?**

I might be able to solve for x given that y is 15 if I had any idea what the equation was.

**la**

Well I suppose your own :)

**math help**

3 < 4 three is less than four 4 > 3 four is greater than three and by the way 4<=4 four is either less than or equal to four

**physics**

31 cos 35

**work and energy PHYSICS**

at O where h = 0, all kinetic, E= (1/2)m Vi^2 + 0 at Q, not moving any more E =0 + m g Q Total energy during whole trip E = (1/2)m v^2 + m g h as h goes up to Q, v goes down to 0 using the start and finish points (1/2) m V^2 = m g Q Vi^2 = 2 g Q Vi = sqrt(2gQ)

**Physics - studying for finals**

for the second part, out in a phase angle .05 sin[(2pi/.75)(x+.375t) -PHI] (2pi/.75)(0.50) -PHI = 0 PHI = 2 pi (.5/.75)

**Physics - studying for finals**

A =0.0500 m L = 0.750 m T = 1/5 = 0.2 goes .75 m in .2 s so v=.75/2 = .375m/s for constant phase (x+vt) the+vt makes it left to make it go 2pi for every wavelength l or time T sin [2 pi (x+vt)/L] now the size .05 sin[(2pi/L)(x+vt)] more numbers in .05 sin[(2pi/.75)(x+.375t)]

**Math**

(x-1)(3x-2)(x-4i) but (x-4i)is not allowed alone, we also need its complex conjugate (x-1)(3x-2)(x-4i)(x+4i) I get 3x^4-5x^3+50x^2-80x+32

**Math**

8x + x = 9 x = 63 x = 7 so 8x = 7*8 which is about 56 as I remember.

**physics**

v = g t = 9.81 * 10 = 98.1 if no air drag but with friction terminal speed is 21 so 21 m/s

**Math**

x = -2 is a vertical line through the point (-2,0). Y can be anything.

**Math (optimization) really confused**

three fences of length x two fences of length y A = xy = 225 so x = 225/y p = total length = 2y + 3 x we want to minimize p p = 2 y +3(225/y) dp/dy = 0 at max or min dp/dy = 0 = 2 -675/y^2 2 y^2 = 675 y^2 = 337 y = 18.4 x = 225/18.4 so what is 2y+3x?

**History Please Help**

They were people, humans.

**Physics**

F * 0.24m = 31Nm so F = 31 Nm/0.24m

**Physics**

try throwing something up and see if time stops and moved backwards while the object falls back down.

**what do you think ?**

The force on this object is F = - m g so a = -g What are your answers?

**Physics**

v = Vi +a t 30 = 10 + 2 t t = 10 seconds but your answers are about distance d = Vi t + (1/2) a t^2 d = 10(10) + 10^2 = 200 m

**Physics**

You are welcome. Remember that figure skater spinning slowly with arms extended, then suddenly speeding up when she pulls her arms in :)

**Physics**

Ip = I of platform =(1/2)(95)(2.4^2) Angular momentum = Ip(2.3) IT STAYS THAT FOREVER New In = Ip +30*(2.4^2) In omega = Ip (2.3) omega = (Ip/In)(2.3) (Part a) b) Her I = mr^2 is zero BACK to original I and 2.3 rad/s c) (1/2) In omega^2 - (1/2)Ip(2.3^2)

**physics**

You are welcome.

**physics**

200 food calories for a half cup so 400 for a whole cup 400 cal (4184 J/cal) = 1,673,600 J watts = 1,673,600 J/600 s = 2789 Watts which is 3.74 hp

**Physics**

height above bottom call it h h = 33(1-cos 31) initial energy = m g h speed at bottom = sqrt(2gh) because (1/2)mv^2 = m g h for part b initial energy = m g h +(1/2)m(25) so at bottom (1/2) m v^2 = that initial energy

**Physics**

LOL, you answered your own question Potential energy = m g h Kinetic energy = (1/2) m v^2 so (1/2) m v^2 = m g h = 73.8*9.81*23.9 Joules (your first answer) so v = sqrt (2 g h) (by the way, remember that. You need it frequently)

**Math**

4 1/3 = 13/3 cans/64 oz = 13 cans/192 oz so 96 oz (13 cans/192 oz) = 6.5 cans

**Math**

Sketch a number line mark them on it like from left to right -13 -7 0 +1 +7

**Algebra 1**

3 y = - 2 x + 12 so y = (-2/3) x + 4 m = -2/3 and b = 4

**History**

You are welcome.

**History**

Oh my ! First check Constitution Amendment 10. Powers not delegated to the US gov. by the Constitution are reserved to the states or to the people (look up exact wording). Local governments do not exist in the Constitution but States reserve powers for them. We are a UNION of ...

**Math**

You are welcome and good luck ! I hope your grandmother comes through all right.

**Math**

To check #1 You say B which is y=3x+6 if x = 6 y = 3(6) + 6 = 18+6 = 24 NO! See, you can check without asking me. y = 18+b y = 8 8 = 18+b b = -10 so the RIGHT answer is y = 3x -10 which is A now slope of first = -3 second is 6y = 2x + 3 , slope = +1/3 second slope = -1/first ...

**Math**

9-t

**Math**

6*37+43 if she always works 37 hours per week income = 6 * 37 + tip otherwise income = 6 * hours + tip

**Physics**

second problem same Newton One stuff.

**Physics**

x momentum = 61.2 * 2.25 FOREVER y momentum = 66.2 * 1.30 FOREVER so final mass = 61.2+66.2 = 127.4 final x momentum : 127.4 * Vx = 61.2*2.25 Remember? final y momentum 127.4 * Vy = 66.2* 1.30 final speed = sqrt(Vx^2+Vy^2) tan theta = Vy/Vx where theta is angle above +x axis

**Algebra 2 Honors**

You are welcome.

**oh my**

My work - 2 = 1/4 ?(100 - h) I multiplied both sides by 4 from - 8 = ?(100 - h) ------------- OK SO FAR BUT square both sides 64 = 100 - h h = 100-64 h = 36 domain from 100-h must be + 0<h<100 for range if h = 0, t = 10/4 hits ground if h = 100, t = 0 drop it then so 0&...

**Thank you Philip**

Thanks :)

**Physics**

3.4 WHAT?? I assume radians/second but hard to say. I will use that but if RPS or something, convert I disk = (1/2)m r^2 so Id = .5*.4*.36^2 and It = .5 * 1.7 * .36^2 initial angular momentum = It*3.4 final angular momentum (the same of course) = It omega +Id omega = omega(It+...