Monday

April 27, 2015

April 27, 2015

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*

**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*