Friday

November 28, 2014

November 28, 2014

Total # Posts: 19,597

**algebra**

1. let z = x^2 then yo have 4 z^2 - 4 z + 1 (2z-1)(2z-1) which is (2x^2-1)(2x^2-1) 2. a^2 (a^2+1)
*October 15, 2014*

**algebra**

(x+3)(x-2) 3*5 = 15 which differs from 113 by 2 so (3x-1)(2x+5)
*October 15, 2014*

**Linear Algebra**

.866 is sin 60 by the way
*October 13, 2014*

**Linear Algebra**

L1 = 1 L2 = -.5 - .866 i L3 = -.5 + .866 i eigenvectors messy see http://www.wolframalpha.com/widgets/view.jsp?id=9aa01caf50c9307e9dabe159c9068c41
*October 13, 2014*

**Algebra 2 Answer Check**

just put in a bunch of cost values from 0 to 10 if the cost were $2 change = 8 cost - change = 2 - 8 = -6 and 10 - 2(8) = -6 It is only non-negative if the cost is between 5 and 10
*October 13, 2014*

**Algebra 2 Answer Check**

I misread it cost = 10 - change cost - change = 10 - 2 change
*October 13, 2014*

**Algebra 2 Answer Check**

Huh f(x) = 10 - x
*October 13, 2014*

**Algebra 2**

You are right, there is no solution to #1
*October 13, 2014*

**Algebra 2**

Oh, I see, you are right. no positive divided by -5 could be + 6
*October 13, 2014*

**Algebra 2**

-26/3 is negative 34/3 is positive but they could both be negative anyway
*October 13, 2014*

**Algebra 2**

By the way to graph that parabola y = 5 x^2 - 8 x + 11/3 http://www.wolframalpha.com/input/?i=5+x^2+-+8x+%2B+11%2F3
*October 13, 2014*

**Algebra 2**

1. (|3x -4|)/(-5) = 6 A: no solution ========================= multiply both sides by - 5 , no arrow business because just an equal sign 3 x - 4 = -30 or -3x + 4 = -30 3 x = -26 or -3x = -34 so there are two solutions
*October 13, 2014*

**Algebra 2**

6. |12 - 4x| - 4 > 20 A: x < -3 and x > 9 ============================ 12 -4 x > 24 or -12 + 4x >24 -4x > 12 or 4x > 36 x < -3 or x > 9
*October 13, 2014*

**Algebra 2 #1 sorry**

1. (|3x -4|)/(-5) = 6 (|3x -4|) = -30 or 3x-4 = -30 or -3x+4 = -30 so x = -26/3 or x = 34/3
*October 13, 2014*

**Algebra 2**

5. (-3) x (|5x - 8|)- 5 greater than or equal to 6 A: no solution? ============================ 3 (-3) x (|5x - 8|)- 5 >/= 6 (-3) x (|5x - 8|) >/= 11 x (|5x-8)| </= -11/3 x(5x-8) </= -11/3 x(-5x+8) </= -11/33 5 x^2 - 8 x </= -11/3 -5 x^2 + 8 x </= -11/3 ...
*October 13, 2014*

**Algebra 2**

4. [(|x - 2|)/ (4) greater than or equal to 5 A: -18 < x < 22 =========================== x-2 >/=20 or -x+2 >/= 20 x >/= 22 x </= -18
*October 13, 2014*

**Algebra 2**

3. |5x + 15| > 20 A: x > 1 and x < -7 5x +15 > 20 or -5x - 15 >20 x > 1 yes -5x > -35 divide both sides by -5 and reverse the arrow x < 7 why the sign ?????
*October 13, 2014*

**Algebra 2**

2. (|2x -5|) = x + 3 A: x = 8 or x = 2/3 ========================= 2x-5 = x+3 or -2x+5 = x+3 x = 8 or x = 2/3 you got that right. Why did you miss #1 ????
*October 13, 2014*

**Algebra 2**

1. (|3x -4|)/(-5) = 6 (|3x -4|) = -30 or 3x-6 = -30 or -3x+6 = -30 so x = -24/3 = -8 or x = 12
*October 13, 2014*

**Math**

2 sin T cos T cos T /sinT = 2 cos^2 T
*October 13, 2014*

**algebra**

a circle with radius 10 and center at (7,6) (x-7)^2 + (y-6)^2 = 10^2 = 100 where does it hit the y axis (y=0) ? (x-7)^2 + 36 = 100 (x-7)^2 = 64 (x-7) = +/- 8 x = 7 +/- 8 if x = 7+8 then x = 15 if x = 7-8 then x = -1
*October 12, 2014*

**Physics**

The lighter one had to be going faster. To be at 45 degrees, momentum north = momentum east 2000 v = 3000 (2v/3)
*October 12, 2014*

**Physics 12**

u = 12 cos 42 = 8.92 m/s the whole time Vi = 12 sin 42 = 8.03 v = Vi - 9.81 t h = 9.5 + Vi t - 4.9 t^2 0 = 9.5 + 8.03 t - 4.9 t^2 t = [ -8.03 +/- sqrt (8.03^2-4*-4.9*9.5)]/-9.81 t = [-8.03+/-sqrt(251) ]/-9.81 t = 2.43 s
*October 12, 2014*

**calculus**

a = area = 6 x^2 da/dx = 12 x so da = 12 x dx
*October 12, 2014*

**calculus**

Again? http://www.jiskha.com/display.cgi?id=1413057054
*October 12, 2014*

**Nonsense**

It is true that in obsolete English units H(t) = Hi + Vi t - (1/2)(32) t^2 if Hi = 72 ft and Vi = 0 then H(t) = 72 - 16 t^2 however your next line makes no sense at all. perhaps you mean when is H = -184 ??? then 72 - 16 t^2 = -184 16 t^2 = 256 t^2 = 16 t = 4 seconds
*October 12, 2014*

**Calculus**

dv = surface area * dh so dv/dt = surface area * dh/dt width at surface = 40 + (80-40)(30/40) = 40 + 30 = 70 cm = 0.70 m so surface area = 9 * .7 = 6.3 m^2 so .3 m^3/min = 6.3 m^2 * dh/dt and dh/dt = .047 meters/min or 4.7 cm/min
*October 12, 2014*

**physics**

time 2 = 1.81 * time 1 h = (1/2)gt^2 so h/t^2 = constant = H1/t1^2 = H2/t2^2 H2/H1 = t2^2/t1^2 = 1.81^2 = 3.27
*October 12, 2014*

**College Algebra**

Yes, but it is trivial p = 0 and p = 10 give R = 0
*October 12, 2014*

**physics**

m g down ramp = m g sin 28 mg normal = m g cos 28 m g sin 28 - mu m g cos 28 = m (.98) sin 28 - mu cos 28 = .98/9.81
*October 12, 2014*

**physics**

potential energy proportional to height, m g H so Hn = (1-.0534)Hn-1 Hfinal = .9466^n Hinitial 2.79 = .9466^n 5.89 .9466^n = .4737 n log .9466 = log .4737 n = 13.6 so 13
*October 12, 2014*

**calculus**

well Diagonal = D = x sqrt 2 so dD = sqrt 2 dx a = x^2 so da = 2 x dx etc
*October 11, 2014*

**physics**

horizontal force exerted = 75 cos 22 +75 cos 32 vertical force exerted = 75 (sin 32 -sin22) normal force on ground = m g - 75(sin32-sin22) friction force = mu (normal force) acceleration = 0 so friction force = horizontal force exerted work done = 13 * friction force You did ...
*October 11, 2014*

**Math**

.12/52 = .002308 so for n weeks 3 = 1.002308^n log 3 = n log 1.002308 n = 476 weeks or 9.16 years
*October 11, 2014*

**Calculus**

v = x^3 729 = 9^3 so x = 9 dv = 3 x^2 dx = 243 dx = 849.285 - 729 etc
*October 11, 2014*

**Calculus**

Hint: http://www.jiskha.com/display.cgi?id=1413053733
*October 11, 2014*

**Trigonometry**

Hint: sin 2a = 2 sin a cos a so what is 3 sin 2a?
*October 11, 2014*

**calculus**

surface area = a = 6 x^2 da/dx = 12 x so if a = 24, x = 2 da = 12 x dx = 12*2 * dx = 24 dx if da = 2.016 then dx = da/24 = .084 (answer part 1) volume = v = x^3 = 8 when x = 2 so dv/dx = 3 x^2 dv = 3 (2^2)(.084) (part b) 100 (dv / v)
*October 11, 2014*

**Education 606**

http://davidmlane.com/hyperstat/z_table.html
*October 10, 2014*

**physicss**

v = Vi + a t Vi = 0 a = -10 so v = -10 t 0 = 1980 + 0 t - (1/2)(10)t^2 5 t^2 = 1980 t = 19.9 seconds so v = -199 m/s
*October 10, 2014*

**equation**

1 1/2 = 3/2 (3/2) / 3 = 3/6 = 1/2
*October 10, 2014*

**equation**

4/3 ---- 3 is 4/9
*October 10, 2014*

**Math**

bobpursley is correct but of the answers listed B is correct. Your course evidently does not do significant figures. yet.
*October 10, 2014*

**Math**

yes
*October 10, 2014*

**Physics**

we do not have your figure.
*October 10, 2014*

**calculus**

series for f(x when a = 0: tan x = tan 0 + sec^2 0 (x) + .... = 0 + 1 x ..... when does x = tan x +/- .1 make a table of x in radians vs tan x
*October 10, 2014*

**Algebra- please help answer**

5 815/1000 6 21/1000 --------------- 11 836/1000 = 11 418/500 = 11 209/250 11.836
*October 9, 2014*

**Algebra**

.75 + .125 + .09 = .965 1.2 - .965 = .235
*October 9, 2014*

**Algebra whoops !**

11 209/250
*October 9, 2014*

**Algebra**

11 836/1000 = 11 209/1000
*October 9, 2014*

**physics**

2*10/d^2 = 4*10/(12-d)^2
*October 9, 2014*

**physics**

component of weight down ramp = 600 sin 30 = 300 pounds
*October 8, 2014*

**No idea**

I have no idea what your jockey experiment is.
*October 8, 2014*

**physics**

http://science.howstuffworks.com/transport/engines-equipment/pulley.htm
*October 8, 2014*

**Physics**

Pulling with component up on block reducing the normal force between block and floor and thus reducing friction force which is maximum of coefficient of friction times normal force.
*October 8, 2014*

**math**

I do not understand. There are only four aces in the pack. If order is not important, then there is only one way.
*October 8, 2014*

**math**

combination of 4 jacks 3 at a time C(4,3) = 4! /[ 3! (4-3)! ] = 4 combination of 4 twos 2 at a time c(4,2) = 4! /[2!(4-2)!] = 3 so 4*3 = 12
*October 8, 2014*

**Math! Please check!**

You are welcome, good luck.
*October 7, 2014*

**Math! Please check!**

Got it ?
*October 7, 2014*

**Math! Please check!**

Yes and yes To remember forever: 1. Hypothesis: If cow , then mammal 2. converse: If mammal,then cow (maybe) 3. inverse: If not cow, then not mammal (maybe) 4. contrapositive: If not mammal, then not cow (true) Make Venn diagrams for the situation :)
*October 7, 2014*

**Math**

http://davidmlane.com/hyperstat/z_table.html
*October 7, 2014*

**math**

(5/4) *120 = 5 * 30 = 150 pennies which is $1.50
*October 7, 2014*

**math(fractions)**

but 90/20 is 9/2 which is 4 1/2 which is 4.5
*October 7, 2014*

**Algebra**

It is going to be ten times as big.
*October 7, 2014*

**Algebra**

how many 125s in 8450 ? 8450 ----- = 67.6 so 67 full rows 125
*October 7, 2014*

**Algebra**

well, we sure seem to be into division :) 384,400 -------- = 110.587 so 111 3476 because .587 is more than half way from 110 to 111
*October 7, 2014*

**Math! Please check!**

I agree with all of your choices.
*October 7, 2014*

**physics**

v = Vi + a t 152 = 0 + 1.35 * 10^4 t but 1.35 * 10^4 = 135 * 10^2 t = (152/135) * 10^-2 = 1.13 * 10^-2 = .0113 seconds
*October 7, 2014*

**What pulley system**

I have no idea what your block and tackle looks like so can not calculate the mechanical advantage. Divide 1000 by the number of parts of the line pulling up on the piano.
*October 7, 2014*

**PHY1015S**

Two of them :)
*October 7, 2014*

**Math**

if you do not know calculus area of surface = pi d^2/4 area of surface * change in height/min = volume/minute pi d^2/4 * .24 m/min = pump rate - leak rate
*October 5, 2014*

**Math**

0.16 c = 4 so c = 4/0.16 = 25 then yes, subtract 4 and get 21
*October 5, 2014*

**Confusing increase in percent**

That is always confusing and the thing to remember is that doubling is 100% increase.
*October 5, 2014*

**Math**

If the result is 400% of the original 100%, then the increase is 300% +100% = doubled +200% = tripled +300% = quadrupled
*October 5, 2014*

**Physics gr. 12**

You went about this correctly. I did not check the arithmetic.
*October 5, 2014*

**Math**

+++++++ 2 x___+ 1_______ 5x-6 / 10 x^2 - 7 x - 6 ++++++ 10 x^2 -12 x +++++++++++++++ 5 x - 6 +++++++++++++++ 5 x - 6 Remainder = 0
*October 5, 2014*

**math**

at t = 0 xA = -20 , dxA/dt = -24 yA = 0, dyA/dt = 0 xB = 0, dxB/dt=0 yB = 0 , dyB/dt = 25 Dx = differnce in x location = 20 + 24 t Dy = difference in y location = 25 t distance = (Dx^2+Dy^2)^.5 distance = [ 400+480t+576t^2+ 625t^2 ]^.5 = [1201 t^2 + 480 t + 400 ]^.5 d distance...
*October 5, 2014*

**solve long divison polynomials**

http://www.jiskha.com/display.cgi?id=1412542641
*October 5, 2014*

**probability;math**

By the way, they were trying to trick you. If the Jack were NOT replaced, there would only be 51 cards when you went to pick the 8. Then it WOULD HAVE BEEN 4/52 * 4/51
*October 5, 2014*

**probability;math**

as long as it is replaced, the events are independent 4/52 * 4/52
*October 5, 2014*

**Physics**

v = Vi + a t Vend = 24 + 35 (1.9) angle at 1.9 s = 1.9(Vi+Vend)/2 total angle = 436 + angle at 1.9 s time at Vend = 1.9 + 436/Vend
*October 5, 2014*

**Math Growth Rate w/ inflation**

1.5 = (1+r)^3 log 1.5 = 3 log (1+r) 1 + r = 1.1447 r = .145 so 14.5 percent 1.08 = 1.1447^n find n continuous 1.5 = e^3k ln .5 = 3 k
*October 3, 2014*

**Physics**

4.92/360 = 500/c c = 36,585 km approximate check a degree on a great circle (around any circumference) of earth is 60 nautical miles :) (1.852 kilometers / naut mile) 360 * 1.852 * 60 = 40,000 close enough
*October 3, 2014*

**Math**

3.647 - 3.003 = 0.644 = 0.6
*October 3, 2014*

**Math (Confused, no idea where to begin)**

if t = 5 2 e^-(.16*5)=2 e^-.8 = 2/e^.8 = .899 = .90 volts 1 = 2 e^-(.16t) ln .5 = -.16 t t = 4.33 seconds at 0 sec V = 2 at 5 seconds V = .90 V = Vi (r)^t .9 = 2 r^5 .45 = r^5 log .45 = 5 log r r = .852 so every second multiply by .85 so decreases by 15% every second
*October 3, 2014*

**error**

parallel to y = 5 x - 6 so slope = 5 so dp/dx = 5 at x = 4 dp/dx = slope(x) = (x-1)(1) + (x+k) (1) = x - 1 + x + k = 2x+k-1 at x = 4, dp/dx = 7+k so 7+k = 5 k =-2
*October 3, 2014*

**CALC AB**

parallel to y = 5 x - 6 so slope = 5 so dp/dx = 5 at x = 4 dp/dx = slope(x) = (x-1)(1) + (x+k) (1) = x - 1 + 1 + k = x+k at x = 4, dp/dx = 4+k so 4+k = 5 k = 1
*October 3, 2014*

**Math**

cos theta = .2
*October 3, 2014*

**Calculous Pre**

I guess by growth rate you mean with yearly compounding and continuous means e^kt if yearly for three years 15 = 11 (1+r)^3 1.3636 = (1+r)^3 log 1.3636 = 3 log (1+r) 1+r = 1.1089 so r = .109 = 10.9 percent now if continuous 1.3636 = e^3k ln 1.3636 = 3 k k = .103 or 10.3 ...
*October 3, 2014*

**Math Calculous Hey**

Hey, I just did two of these, please use one name and do not ask me to do a whole bunch of virtually identical problems.
*October 3, 2014*

**Pre-Calc**

a b^t = 2 e^(8t) ln a + t ln b = ln 2 + 8 t a = 2 and ln b = 8 so b = e^8 = 2980 so I agree
*October 3, 2014*

**physics**

Fn = 62.6 Fw = 45.9 |F| = sqrt (62.6^2+45.9^2) = 77.6 angle north of west = tan^-1 (62.6/45.9) = 53.8 degrees so to cancel that 77.6 at 53.8 south of east
*October 3, 2014*

**PHYSICS**

work = force * distance in direction of force 2.5*10^-4 = .36 x x = 6.9*10^-4 meters
*October 3, 2014*

**Physics**

I will assume he just stops the descent of the ball change of ball velocity = 29 m/s a = change of velocity/time = 29/(16*10^-3) = 1.81 * 10^3 m/s^2
*October 3, 2014*

**Physics**

F = G Mm/r^2 F = m a = m v^2/r so G M m/r^2 = m v^2/r v^2 = G M/r G M same for both va^2 ra = vb^2 rb but va = 82 vb 6724 vb^2 ra = vb^2 rb so rb = 6724 ra circumference = 2 pi r period = circumference / v = 2 pi r/v period a = 2 pi ra/82 vb period b = 2 pi 6725 ra/vb 1/82 / ...
*October 3, 2014*

**CALCULOUS**

1.043^n = 2 n log 1.043 = log 2 n = log 2/log 1.043 = 16.5 years
*October 3, 2014*

**Science**

http://www.jiskha.com/display.cgi?id=1412288943
*October 2, 2014*

**Very important**

Go back and read my reply about the bottles moving at constant velocity !!!!
*October 2, 2014*

**Science**

a = 2 (1.5)/3.6^2
*October 2, 2014*

**sign error**

-h/h or -1
*October 2, 2014*

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