Wednesday

September 2, 2015
Total # Posts: 21,878

**physics**

i = Q/t or amps = coulombs/second you do not need the electron charge for this - red herring intended to confuse you.
*April 24, 2015*

**DISCRETE MATH**

p fail = .2 p pass = .8 p five pass = .8^5 = .32768
*April 24, 2015*

**physics**

n * electron chsrge = 3.2*10^-6 Coulombs
*April 24, 2015*

**AP CALC**

d^2f/dx^2 <0 in other words curves down, sheds water
*April 24, 2015*

**Math**

6 sprinters 3 at a time but ORDER matters so we are talking permutations not combinations n!/(n-r)! = 6!/3! = 6*5*4 = 120
*April 23, 2015*

**Chemistry**

6.02*10^23 molecules/mol so 40.79kJ /6.02*10^23 molecules times I suspect you mean 8.51*10^10 molecules 40.79 (8.51/6.02)10^(10-23) 57.66 * 10^-13 or 5.766 * 10^-12 kJ
*April 23, 2015*

**no idea**

I have no idea what our experiment is.
*April 23, 2015*

**Algebra**

when y = 0 , x = 6 0 = 6m + b b = -6m so for the second one y = 3mx -6m when y = 0 6 m = 3 m x x = 2
*April 23, 2015*

**Math Help**

26 letters - 2 = 24 letters choice of 24 letters for first letter since letters can be repeated we have 24*24 = 576 letter combinations now we have ten numbers, 0 through 9 again they can be repeated (AA0000 is allowed) 10^4 = 10,000 so 576 * 10,000 = 5.76 * 1,000,000 = 5,760,000
*April 23, 2015*

**Math**

2^15 32768
*April 23, 2015*

**Math 222**

-x^2 + 3 x + 5 = 0 x^2 - 3 x - 5 = 0 x = [ +3 +/- sqrt(9 + 20) ] / 2 1.5 +/- 2.69
*April 23, 2015*

**Math 222**

a^2 - 6 a + 9 = 0 (a-3)(a-3) = 0 a = 3 or a = 3, in other words the vertex is on the x axis.
*April 23, 2015*

**Math 222**

a^(1/3) a^(3/2) a^(-1/2) a^ [ 1/3 + 3/2 -1/2 ] a^[1 1/3] or a^(4/3)
*April 23, 2015*

**Geometry**

V = k x^3 A = c x^2 for big one xb^3 = 1331/k for small one xs^3 = 216/k or xb/xs = (1331/216)^(1/3)= 1.83333333.... so xb^2/xs^2 = area ratio = 3.361111.... 484/3.361111... = 144
*April 23, 2015*

**World History**

alliances
*April 23, 2015*

**SOCIAL STDIES HELP!**

We checked all three.
*April 23, 2015*

**SOCIAL STDIES HELP!**

1. agree - roaring 20s until Oct 1929 2. NOT TV - happened when I was in elementary school LOL Electricity yes. stuff like washing machines was mostly after WW2. I remember rollers turned by hand to squeeze water out of laundry from tub. I suppose you could count that in which...
*April 23, 2015*

**Math 222**

eighth root of a^7
*April 23, 2015*

**Math 222**

sqrt 50 or sqrt(50 x^3) ?????? I will assume sqrt (50 x^3) 4 u sqrt(2*25) x sqrtx - x sqrt(2*16) sqrtx * u 20 u x sqrt(2x) - 4 u x sqrt(2x) 16 u x sqrt(2x)
*April 23, 2015*

**Physics**

first use conservation of momentum to get swing speed at bottom Vswing = Vbird (Mass bird/Mass swing) then m g h = (1/2) m Vswing^2 or h = Vswing^2/(2 *9.81)
*April 23, 2015*

**Math**

each term is half the previous one 1.6 *.5^(n-1) is a geometric sequence
*April 23, 2015*

**Precalculus**

in other words y = 4(n-1) = 4x - 4
*April 23, 2015*

**Precalculus**

(n+1,4n) from n = 0 to n --->oo seems to work
*April 23, 2015*

**chemistry**

NaNO3 = 23 + 14 + 3(16) = 85 g/mol 2.528/85 = .03 mol *1000 mL/.503mol = 59.1 mL
*April 22, 2015*

**chemistry**

.516 * 111.5/1000
*April 22, 2015*

**precalculus**

y^2 - 2 y = -x You were asked to eliminate the parameter t, not to solve for y. However I do not know the traditions of your particular group :)
*April 22, 2015*

**precalculus**

t^2 = 1-x t = y-1 so t^2 = y^2-2y+1 so y^2-2y+1 = 1 - x
*April 22, 2015*

**math**

http://www.jiskha.com/display.cgi?id=1429755553
*April 22, 2015*

**Math**

Draw it !!!!! call missing point P slope XY = (-2-6)/(5+1) = -8/6 =-4/3 so for XY y = -(4/3) x + something BUT WP has same slope y = -(4/3) x + b 3 = -(4/3) (-5) + b b = 3 - 20/3 = -11/3 3 y = -4x - 11 is WP Find YP the same way it is parallel to XW then find intersection of ...
*April 22, 2015*

**Math**

25*15 = 375 ft^2 1 yd = 9 ft^2 so 375/9 = 41 2/3 yd^2 41 2/3 * 20 = $833.33 no way , use cheaper carpet and install it yourself !
*April 22, 2015*

**math**

On a three day hike, Robert hiked twice as many miles on the first day as on the second day. On the third day he hiked 5 miles. Carlos hiked 5 miles on the first day and three times as many miles on the second day as on the third day. (a) Write and simplify an expression for ...
*April 22, 2015*

**pre-calculus**

t^2 = 1-x t = y-1 so t^2 = y^2-2y+1 so y^2-2y+1 = 1 - x
*April 22, 2015*

**pre-calculus**

hey, just pick some points note x^2+y^2 = r^2 = circle
*April 22, 2015*

**pre-calculus**

because I learned in a trig course the sin^2 x + cos^2 x = 1
*April 22, 2015*

**pre-calculus**

x = 1 + cos t y = 1 - sin t cos t = (x-1) sin t = (1-y) cos^2 t = (x-1)^2 sin^2 t = (1-y)^2 ----------------- add 1 = (x-1)^2 + (1-y)^2 your turn :)
*April 22, 2015*

**Math**

same slope (6-9) / (5+4) = (-1-y) / (-3-3)
*April 22, 2015*

**math typo I think**

I see Robert and Carlos but who is Matt?
*April 22, 2015*

**Math**

P is (0,T) slope of CD = 2/-3 = -2/3 slope of PC is then 3/2 so PC is y = (3/2)x + b at C, x = -3 and y = -6 -6 = 1.5 (-3) + b b = -6 + 4.5 = -1.5 so y = 1.5 x - 1.5 on the x axis when y = 0 x = 1 sp P at (1,0)
*April 22, 2015*

**Math**

2 = (0-12)/(a-4)
*April 22, 2015*

**history of math**

You are welcome.
*April 22, 2015*

**history of math**

s = 2 w w = 2 d so s = 4 d w = 2 d 4 d + 2 d + d = 100 7 d = 100 so d = 100/7 (not the wife) check if d = 100/7 w = 200/7 and s = 400/7
*April 22, 2015*

**Problem solving**

a + b = 7869 a - b = 1879 ------------ add 2 a = 9748 a = 4874 then b = 7869-4874 = 2995
*April 22, 2015*

**algebra 2**

s + a = 358 so s =358-a 1.5 s + 3.25 a =752.25 1.5(358-a) + 3.25 a = 752.25 find a then s
*April 22, 2015*

**7th grade math**

all correct 4. ratio of model to full scale is 1/25 1/25 = 3.8/h h = 25 * 3.8 = 95 yes
*April 22, 2015*

**calculus**

same as your fence really a + b = 40 so b = 40 - a P = a b = a(40-a) = 40 a - a^2 dP/da = 40 - 2 a a = 20 then b = 20 so 20 and 20
*April 22, 2015*

**PHYSICS**

well we agree on part a and part b is easy
*April 22, 2015*

**PHYSICS**

http://www.jiskha.com/display.cgi?id=1429748458
*April 22, 2015*

**calculus**

p + 2 q = 800 so p = 800 - 2 q A = p q = (800 - 2q)q A = -2 q^2 + 800 q now you could find the vertex of this parabola easily with Algebra 2 by completing the square but you said calculus so dA/dq = 0 at max = -4 q + 800 or q = 200 then p = 800 - 400 = 400 so A = 80,000 ft^2 ...
*April 22, 2015*

**PHYSICS PLEASE HELP**

http://www.jiskha.com/display.cgi?id=1429748458
*April 22, 2015*

**PLEASE HELP**

sorry, had to drop further to make up for friction m g h = -1902 -187 = -2089 Joules and h = 2089/(60.8*9.81)
*April 22, 2015*

**PLEASE HELP**

He must have been heading downhill ! change in kinetic energy = (1/2)(60.8)(8.12^2 - 1.84^2 ) = 1902 Joules energy in = -278 + 90.8 = -187.2 h = 0 initially m g h = - 1902 + 187 = - 1715 Joules h = -1715/(60.8*9.81) = - 2.88 meters so 2.88 is absolute value
*April 22, 2015*

**Pre-Calculus**

think 14 x^2/56y^3 = (14/56)(x^2/y^3)
*April 22, 2015*

**Pre-Calculus**

sure (2/4) of anything is (1/2) of anything
*April 22, 2015*

**Pre-Calculus**

14/56 = 1/4
*April 22, 2015*

**math**

integral ln x / x = (1/2)(ln x)^2 because d/dx (ln x)^2 = 2 ln x (1/x) you can do the rest
*April 22, 2015*

**calculus**

x is + over the interval so the function we want to integrate is always + over the interval when you see something squared on the bottom think: d/du (v/u) = [ u dv/du - v ] / u^2 so here let u = (3x+1) if v were 1 d/du(v/u) = [0-3]/(3x+1)^2 so let v = -1/3 and integral = -(1/3...
*April 22, 2015*

**Physics**

Moments about center of yoyo shaft torque = 2*(.5/100) = .01 NM omega = alpha * t but alpha = Torque/ I so omega =Torque * t/I or I = Torque * t / omega = .01 * 5 / 15 ========================= angle = (1/2) alpha t^2 ============================ now for part c I assume you no...
*April 22, 2015*

**Math**

a ton is 2000 pounds in English as opposed to metric or shipping units. I suspect you want the 2000 pound ton then 7 tons is 14,000 pounds so 14,000 / 40 = 1400/4 =?
*April 22, 2015*

**Science**

The wiki article is pretty good on this subject: http://en.wikipedia.org/wiki/Thermocouple
*April 22, 2015*

**Math**

you are looking for the least common multiple of 252 and 408 The way I do such problems is to factor each 252 = 2*126 = 2*2*63 = 2*2*3*21 = 2*2*3*3*7 then 408 = 2*204 = 2*2*102 = 2*2*2*51 so we need 2*2*2 * 3*3 * 7 * 51 = 8*9*7*51=25704 check 25704 / 252 = 102 blue 25704 / 408...
*April 22, 2015*

**Math**

(Y2-Y1) / (X2-X1) for example (-2-4)/(2 - -1) = -6/3
*April 22, 2015*

**Chemistry**

Dr Bob told you much more precisely than I how do do this sort of problem. I suggest just doing them. by the way, your book or Google will tell you how many grams of any element are in a mol. for example for H about 1 for O about 16 for C about 12 etc Do you not have a ...
*April 22, 2015*

**If you answer these questions I will pass this cla**

I assume all problems are at STP where a mol of gas is 22.4 Liters
*April 22, 2015*

**If you answer these questions I will pass this cla**

Hint, convert grams to mols
*April 22, 2015*

**Trig**

yes, about 1.3 radians
*April 22, 2015*

**Trig**

I assume you mean y = 7 cos θ + 24 sin θ well, my inclination is to look for where the derivative is 0 dy/dθ = -7 sin θ + 24 cos θ = 0 or tan θ = 24/7 = 3.43 θ = 73.7 degrees
*April 22, 2015*

**AP Physics**

Steve tried to answer earlier but you have still not given direction of velocity vector of the first ball. Anyway as he said conserve momentum in the north direction and in the east direction.
*April 18, 2015*

**Physics**

hmmm, that flat earth assumption again ! 60 = (1/2)(9.81) t^2
*April 18, 2015*

**Vectors**

x = -2 + 2 s y = 3 + 3 s z = 1 - s on the y axis, x and z are 0 0 = -2 +2 s 0 = 1 - s so it is where s = 1 then y = 3+3 = 6 so (0 , 6 , 0 )
*April 18, 2015*

**Math - use flat earth**

earth flat at this range :)
*April 17, 2015*

**Vectors**

Beats me Ryan
*April 17, 2015*

**Vectors**

find slope of perpendicular original is slope = -1 so slope of perpendicular is -1/-1 = 1 pick a point on line 2, like (0,0) then equation of perpendicular through that point is y = x (just to make it east) where does y = x hit the first line? 2 x + 2 x = 16 x = 4 then y = 4 ...
*April 17, 2015*

**PRE - CALCULUS**

I do not have time NOTE in your previous question, the determinant of the 3 by 3 coef matric is zero, can not solve.
*April 17, 2015*

**DETERMINANT = 0**

calculate the determinant of the 3 by 3 on the left as if you were going to do Cramer rule THE DETERMINANT IS ZERO
*April 17, 2015*

**PRE - CALCULUS**

Huh, they are 4 -1 3 12 1 4 6 -32 5 3 9 20 the trouble is that it can not be solved
*April 17, 2015*

**PRE - CALCULUS**

You mean this ? 17y+21z = -140 that would be 0 17 21 -140
*April 17, 2015*

**PRE - CALCULUS**

You can not reduce the last row to 0 0 1 something
*April 17, 2015*

**PRE - CALCULUS**

1 4 6 -32 yes but your problem gives a very strange answer
*April 17, 2015*

**PRE - CALCULUS**

http://www.idomaths.com/gauss_jordan.php
*April 17, 2015*

**PRE - CALCULUS**

4 -1 3 12 1 4 6 -32 5 3 9 20 Step 1: Swap row 3 and 1 5 3 9 20 1 4 6 -32 4 -1 3 12 Step 2: Divide row 1 by 5 1 0.6 1.8 4 1 4 6 -32 4 -1 3 12 Step 3: Subtract row 1 from row 2 1 0.6 1.8 4 0 3.4 4.2 -36 4 -1 3 12 Step 4: Subtract (4 × row 1) from row 3 1 0.6 1.8 4 0 3.4 4...
*April 17, 2015*

**PRE - CALCULUS**

I think they gave you Sk k(3k-1)/2 Sk+1 = Sk + 3 (k+1) - 2 = (3 k^2 - k)/2 + 3 k +1 = (1/2)( 3 k^2 - k + 6 k +2 ) = (1/2)(3 k^2 + 5k + 2) = 1.5 k^2 + 2.5 k + 1
*April 17, 2015*

**chemistry**

same as last one I just did
*April 17, 2015*

**Chemistry**

molar mass of Mg(OH)2 = 24.3+2*17 = 58.3 g so we have .605/58.3 = .0104 mol molar mass of H2SO4 = 2+32+64 = 98 g so we have 1/98 = .0102 mol so we will get .0102 mol of MgSO4 .0102 ( 24.3+32+64) = 1.23 g
*April 17, 2015*

**PRE - CALCULUS**

You are welcome.
*April 17, 2015*

**PRE - CALCULUS**

S1 = 1(4)/2 = 2 check S2 = 2+5 = 7 = ? 2(7)/2 = 7 check S3 = 7+8 = 15 = ? 3 (1+9) /2 = 3*5 = 15 check
*April 17, 2015*

**Calculus**

I do not know - ask teacher. Unless we made arithmetic errors, that should be right. Perhaps in terms of pi or something ?
*April 17, 2015*

**Calculus**

we had A = 15.5 D - .897 D^2 and we know D = 8.64 A = 15.5 (8.64) - .897(8.64^2) = 67 ft^2
*April 17, 2015*

**Calculus**

h is height of rectangle1 31 = 2 h + D + pi D/2 2 h = 31 -D(1+pi/2) h = 15.5 - (D/2) (1+pi/2) area = D h + (1/2)(pi D^2/4) A = D (15.5 -1.29 D) + (1/8)pi D^2 A = 15.5 D - .897 D^2 dA/dD = 0 at max = 15.5 - 1.79 D D = 8.64 ft then h = 4.4 ft check my arithmetic !
*April 17, 2015*

**Math 222**

assume your x means * or "times"? multiply --- add exponents raise to power - multiply exponents a^.25 b^.5 * a^1 b^.5 a^1.25 b^1 or a^(5/4) b
*April 17, 2015*

**calc**

first second a = change in V/change in t = 29.32/1 second second a = (50.82-29.32) /1
*April 17, 2015*

**math**

6!/(6-2)! = 6*5 = 30 yes 8!/ [ 5! (3!) ] = 8*7*6/(3*2) = 56 sure enough
*April 17, 2015*

**math**

26.19/2845 = .0092056 times 365/12 = .28 times 100 = 28 %
*April 17, 2015*

**physics**

r = mv/qB double r ---> double v
*April 17, 2015*

**Vectors**

I assume this is three dimensional y (3x+1) = 0 y = 0 is a plane and x = -1/3 is a plane
*April 17, 2015*

**physics**

So, what do you think?
*April 17, 2015*

**math**

2 L + 2 w = 29 L = 1 + 2 w so 2 + 4 w + w = 29 5 w = 27 I have a sneaking suspicion that you have a typo because the text writers always make this stuff come out whole numbers.
*April 17, 2015*

**Physics**

eyes to mirror bottom to sole of shoe. They do not ask about top of mirror and top of head :)
*April 17, 2015*

**physics**

-9.81 m/s^2 0 = 20 - 9.81 t then h = 20 t - 4.9 t^2 or (1/2) m v^2 = m g h so h = v^2/2g
*April 17, 2015*

**physics**

m (v^2/r - 9.81)
*April 17, 2015*