Monday
April 27, 2015

Posts by Damon


Total # Posts: 20,993

Math
I assume x/(x^2-3x-4) - 4/(x+1) ????? x/[(x+1)(x-4)] - 4(x-4)/[(x+1)(x-4)] -3x+4 /[(x+1)(x-4)] blows up if x = -1 or x = 4
January 7, 2015

algebra 2
(x+4)(x-1) = 0 y = x^2 + 3 x - 4
January 7, 2015

math
.4 * 50 = 20
January 7, 2015

Math
x = x^2 + xy + x + y 0 = x^2 + y (x+1) y = -x^2/(x+1)
January 7, 2015

math
1 1/4 = 5/4 bags 7 1/2 = 15/2 pounds /bag so (5/4) bags *(15/2) pounds/bag = 75/8 = 9 3/8 pounds
January 7, 2015

math
365.75 km ( 1 hr/133 km) = 2 3/4 hr = 2 hours and 45 minutes
January 7, 2015

Chemistry
F2O3 ??? 2Fe2O3 + 3C --> 4Fe + 3CO2 ??? maybe mols of Fe2O3 = 3.79*10*24 /6.02*10^23 = 6.30 mols Fe2O3 or 12.6 mols Fe Fe is 56 g/mol so 12.6 * 56 = 706 grams Fe `
January 7, 2015

Math
sin 24 = h/30 h = 30 sin 24 = 12.2 ft note - do not climb ladder that barely reaches the eaves.
January 7, 2015

Physic
c = q/v same q on each, call it q so c1 V1 = c2 V2 so V2 = (c1/c2) V1 and V1 + V2 = 1000 V1 + (c1/c2)V1 = 1000 but c1/c2 = 3/6 = .5 so 1.5 V1 = 1000 V1 = 667 V2 = 333 I think you can go back and get q = v c for each
January 7, 2015

Maths
a + d (n-1) a + d = 7 a + 4 d = 22 ------------ -3 d = -15 d = 5 so a = 2 2 , 7 , 12 , 17 , 22
January 7, 2015

math
6 / (1/3) = 6 * 3
January 7, 2015

physics
force = change in momentum/time = (50 kg * 5000 m/s) /s = 250,000 Newtons thrust weight = m g = 60,000*9.81 = 588,600 N no way
January 7, 2015

physics
m = 30/9.81 a) (30/9.81)v = .005 * 300 b) (730/9.81)v = .005 * 300
January 7, 2015

math
4.5 in ( 20 mi/in) = 90 miles 90 miles (1 in/18 mi) = 5 inches
January 6, 2015

physics
(1/2) m v^2 start = m g h at top so m g h = 2 * 10^4 m = 2*10^4 / (9.81*50) = 40.8 kg
January 6, 2015

Science
Probably with carbon 14 dating. http://dwb4.unl.edu/Chem/CHEM869Z/CHEM869ZLinks/www.all.mq.edu.au/online/edu/egypt/carbdate.htm
January 6, 2015

physics
5.72*10^3 * 3.11 * 10^3 = 17.8 * 10^6 = 1.78 * 10^7 Joules
January 6, 2015

Math
30/20 = 1.5 , 90/60 = 1/5 the same 15/20 = 3/4 , 10/15 = 2/3 NOT the same
January 6, 2015

Math
I would say A
January 6, 2015

Science
You are welcome
January 6, 2015

Science
Yes
January 6, 2015

Math
a + d(n-1) a + d (2) = 1985 a + d(7) = 2015 ----------------subtract 0 - 5 d = - 30 d = 6 a + 12 = 1985 a = 1973 1973 + 6(14) = 2057
January 6, 2015

physics
normal force down = 18.4*9.8 - 126 sin 34.1 so friction force = .123 (18.4*9.8-126 sin 34.1) work done by friction - friction force * 20 meters
January 6, 2015

Science
Yes That is all per molecule.
January 6, 2015

4th grd math
3*8 = 24 fish per day 2.5 * 8 = 16 + 4 = 20 eaten so 4 left over each day I guess you do not have seagulls where you live :)
January 6, 2015

Math
15 sandwiches /.75 hr * 3 hr = 60 sandwiches
January 6, 2015

Science
You are welcome.
January 6, 2015

Science
I mean (6/18)*10^23 atoms/gram
January 6, 2015

Science
2 hydrogens, one oxygen in a molecule so three atoms per molecule a mol is 6*10^23 molecules so 18 * 10^23 atoms per molecule a mol weighs 2+16 = 18 grams so (6/18) * 10^23 molecules per gram
January 6, 2015

math
sorry, yes
January 6, 2015

math
39 - 15 = 25 spaces so 25,000 feet 10:11- 10:05 = 6 minutes 25,000/6 = 4167 feet/min a little less than a mile a minute or 60 miles per hour
January 6, 2015

math
1/4 inch to the foot so one inch = 4 feet 6*4 = 24 feet
January 6, 2015

math
14/10 = 1.4 lions per tiger or 14/24 = 7/12 lions (not loins I assume) and 10/24 = 5/12 tigers
January 6, 2015

algebra
there will be a short time on the way up to 28 and a long one for the way down, we want the second minus the first when will h = 28 feet? 28 = 4 + 56 t -16 t^2 16 t^2 - 56 t + 24 = 0 2 t^2 - 7 t + 3 = 0 (2t-1)(t-3) = 0 t = .5 or t = 3 so t = 2.5 seconds above 28
January 6, 2015

Math
dollars / t shirts = dollars per t shirt A 40/16 = 2.50 per shirt B 140/84 = 1.67 per shirt
January 6, 2015

Math
You are welcome.
January 6, 2015

Math
7 d - 4 d - 32 = -8 3 d = 24 d = 8
January 6, 2015

math
oh, I assumed that the 23 was a typo and it meant 2/3
January 6, 2015

math
I think you added 6 girls and get 20 out of 30
January 6, 2015

math
Rodger is right
January 6, 2015

math
3/7 7+10+7 = 24 total students 14 are girls so 14/24 = 7/12 suspect you mean 2/3 are girls (14+x) /(24+x) = 2/3 42 + 3 x = 48 + 2x x = 6 more girls
January 6, 2015

Math
" it is also perpendicular line" should be it is at the intersection of two perpendicular lines.
January 6, 2015

math
I guess. There are lots of ways to do it actually.
January 6, 2015

math
6 * 5^2 = 6 * 25 = 600/4 = 150 12* 5^3 = 12 * 125 = 1500 1500 * 150 = 225,000
January 6, 2015

math
The one with a right angle.
January 6, 2015

Physics
(1/2) m v^2 = m g h so v = sqrt (2 g h) = sqrt (2*9.81*4)
January 6, 2015

Math
4 * 4.5 = 18 pineapple 8 * 4.5 = 36 orange 12 * 4.5 = 54 seltzer
January 6, 2015

Math
I mean multiply each number of cups by 4.5
January 6, 2015

Math
4+8+12 = 24 cups 108/24 = 4.5 so multiply each number of cups by 6 to get 108 cups Note, a serving is evidently not a cup because 24 cups is 18 servings. I do not know if this is an intentional confusion or a typo.
January 6, 2015

Math
I agree with you.
January 6, 2015

civics
Protect all citizens in time of trouble***
January 6, 2015

civics
I agree with you. The last.
January 6, 2015

civics
I agree, although I am tempted by the first choice :)
January 6, 2015

Physics
http://www.jiskha.com/display.cgi?id=1420573371#1420573371.1420574332
January 6, 2015

Physics again?
Just did that
January 6, 2015

Physics
I will have to assume that it goes the entire 100 meters during this deceleration and crashes into the moon at .5 m/s -.5 = -20 + a t 100 = -20 t + .5 a t^2 a = (-.5+20)/t -100 = -20 t + .5 (20-.5) t 100 = 20 t -9.75 t t = 9.75 seconds to slow down (part b) a = +2 up (part a...
January 6, 2015

Civics
You are welcome.
January 6, 2015

Civics
To ensure the powers of each branch of government are limited and checked by another branch
January 6, 2015

Math
600 - 280 = 320 100 (320/600) = 53.33
January 6, 2015

Math
time = distance/speed 5/(x/5) + 30/(5x) + 20/x = 25/x + 6/x + 20/x = 51/x she has gone 5 + 30 + 20 = 55 km b) 2 = x/5 so x = 10 and time = 51/10 = 5.1 hr c) 40 = 5x x = 8 time = 51/8 = 6.375 difference = 6.375 - 5.1 = 1.275
January 6, 2015

Bosaso
http://davidmlane.com/hyperstat/z_table.html
January 6, 2015

Physics
u = 53/2 = 26.5 m/s forever v = Vi - 9.81 t h = Vi t - 4.9 t^2 = 54 =Vi(2)-4.9(4) or 54 = 2 Vi - 19.6 so Vi = 36.8 m/s ========================== at top, v = 0 0 = 36.8 - 9.81 t t = 3.75 seconds at top but we know u = 26.5 m/s so D = u t = 26.5 * 3.75
January 6, 2015

mechanics and heat
2 v^2 = 100 v = 10/sqrt 2 = speed of 2 kg mass 4 (10/sqrt 2) = .4 V V = 100/sqrt 2 speed of small mass (1/2)(.4)(10,000/2) = 1,000 = Ke of little mass
January 6, 2015

Physics
70*5 - 5*20 = 75 v
January 5, 2015

Physics
increase of length = L *coefficient of expansion * 30
January 5, 2015

Algebra
1.35 s + 1.85 t = 1.65 * 20 s + t = 20 so s = (20-t) =========================== 1.35 (20-t) + 1.85 t = 33 solve for t, go back and get s
January 4, 2015

math/compound
40 periods at a rate of .0615/4 2500 (1.015375)^40=2500(1.841) = $4602.55
January 3, 2015

physics
since you did not specify the direction very well (41 deg from horizontal or vertical? up or down from horizontal? Up or down from vertical?) I will have to be very general in the answer. Vi = 9.66 sin or cos or -sin or -cos of 41 v = Vi - g t at top v = 0 0 = Vi -9.81 t so t...
January 3, 2015

Algebra2
g = -32 ft/s^2 in the feet (old American - English) system so (1/2)g = -16 Watch out, most of us use metric units g = -9.81 m/s^2 in which case h = Hi + Vi t - 4.9 t^2
January 3, 2015

Math
y = -3x - 4n slope = m = -3 y axis intercept, b, is y when x = 0 which is -4n
January 1, 2015

Physics
If the block moves .40 meters then the line is pulled 5 * .4 = 2 meters (a) the work done by the puller person on that line is W in = 60 N * 2 meters = 120 Joules (b) the useful work done on the block was to lift it .40 meters work out = m g h = 25 * 9.81 * .4 = 98.1 Joules so...
January 1, 2015

Physics
The basic form of Newton's second law is Force = rate of change of momentum = change of (m V) /time if m is constant this is the familiar form F = m dV/dt = m A but here it is simple to use the more fundamental form change of momentum/time = m v/t = 1 *5/5 Newtons as ...
January 1, 2015

science
strain proportional to stress
January 1, 2015

science
I am not sure where the fulcrum is but if it is in the middle then: 20 * 5 = 30 * x x = 5(2/3) = 10/3 from center which is 10/3 + 5 from the boy which is 25/3 = 8 1/3 meters from the boy
January 1, 2015

physics
R1 = 13/3 = 4.33 m R10 = 2 m T = 5 seconds / 10 waves = .5 s f = 1/T = 2 Hz wavelength = (4.33-2)/9 = .259 meter v = .259/.5 = .518 m/s
January 1, 2015

physics
Only one where the ball fires a rocket after hitting the floor :)
January 1, 2015

Calculus
You are welcome.
December 31, 2014

Calculus
f" = [(-1)(x+1)^3 - 3(1-x)(x+1)^2]/(x+1)^6 = [-(x+1)+3(x-1)]/(x+1)^4 ( I don't understand how you got this!!) Looks like division of top and bottom by (x+1)^2 and also -(1-x) = + (x-1)
December 31, 2014

Algebra
You are welcome :)
December 31, 2014

Algebra
These problems are pretty advanced for class that has not reached logarithms.
December 31, 2014

Algebra
hmmm well, you need 2^something = 1000 2^3 = 8 2^4 = 16 2^5 = 32 2^6 = 64 2^7 = 128 2^8 = 256 2^9 = 512 2^10 = about 1000 so d = about 10 so 2*10 = 20 days. It said approximate :)
December 31, 2014

Algebra
take the log to any base of both sides for example base 10 log 1000 = d log 2 d = 3/.301 = 9.96 2 day periods or 20 days check my reply to your earlier efficiency problem
December 31, 2014

Algebra-Check my answer please!
5.9 * 10^12 miles/year *2.2 * 10^6 years = 12.98 * 10^18 = 1.298 * 10^19 I get
December 31, 2014

Algebra
up to the left, and up to the right d^2 = (2-a)^2 + (1-7)^2 d^2 = 45 = 4 - 4 a + a^2 + 36 5 = a^2 - 4 a a^2 - 4 a - 5 = 0 (a-5)(a+1) = 0 a = 5 or a = -1
December 31, 2014

Physics
You are welcome.
December 31, 2014

Physics
LOL, yes, depends on purity of water etc. Those numbers are the same to me :)
December 31, 2014

Physics
water is 4186 Joules/kg deg C 110,000 kg 8 deg C so heat out into water = 4186*110,000*8 = 3.68 * 10^9 Joules into water electricity in = 150,000 * 28 * 3600 = 1.51*10^10 Joules efficiency = out/in = .368/1.51 = .244 = 24.4 %
December 31, 2014

Physics
If you understand 2, I think you can do 3 You need to look up heat capacity of water in Joules/kg deg C
December 31, 2014

Physics
2. 1 watt hr = 3600 watt seconds or Joules so 2.0 Mwh = 7200 MJ 33 MJ/kg * m in kg *.18 = 7200 MJ m = 1212 kg
December 31, 2014

Physics
electrical work in = 180,000 *120 = 21.6 *10^6 Joules mechanical work out = 10,500*9.81*218 = 22.5 *10^6 Joules magic? on moon? let's see ? 10th floor about 9 * 3 meters high or 27 meters, not 218 meters
December 31, 2014

Graphing
(2+3)/(-5-3) = (y+3) / (x-3) 5/-8 = (y+3) / (x-3) 5 x -15 = -8 y -24 5 x + 8 y = -9 5+8-9 = 4
December 31, 2014

Chemistry missing data
same amount of what ?
December 31, 2014

Algebra
(-3-7)/(5+2) = (a-7)/(3+2) -10/7 = (a-7)/5 etc
December 31, 2014

Algebra
second function, the one in the table, when x goes up 2, y goes up 4 always so y = (4/2) x + b = 2x+b when x = 1, y = 5 so 5 = 2(1) + b b = 3 so y = 2 x + 3 both of your functions are straight lines that go through (0,3) the original one has slope = 4 the second one has half ...
December 31, 2014

calculus
Good luck :)
December 31, 2014

calculus
Approximate ³√26 by using an appropriate linearization. y = x^(1/3) we know that if x = 27, y = 3 so I will start there. Of course you could do something else. dy/dx = (1/3) x^-2/3 at x = 27 dy/dx = (1/3) /9 = 1/27 = m so y = (1/27) x + b 3 = (1/27)(27) + b b = 2 so...
December 31, 2014

calculus
b should come out just like a :)
December 31, 2014

calculus
y = m x + b at (25,5) 5 = m (25) + b what is m, the slope, there? y = x^.5 dy/dx = .5 x^-.5 = .5/5 = .1 = m so 5 = .1 (25) + b 2.5 = b so our line through (25,5) is y = .1 x + 2.5 now if x = 26 y = 2.6 + 2.5 = 5.1 that is part a check it sqrt 26 = 5.099 Awful close !!! :)
December 31, 2014

physics
v = 10 t = 30 m/s = 3000 cm/s
December 30, 2014

physics
F = C coef v^2 (some area) if there is flow separation probably the cross sectional area is the important one pi r^2 if there is little flow separation then maybe surface areas 4 pi r^2. coefficients for spheres are shown both ways they may want you to say F = (6 pi)coef of ...
December 30, 2014

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