# Posts by Damon

Total # Posts: 29,984

**SAT Math Question?**

L --- 1/3 job/hr S ---1/5 job/hr together 1/3 + 1/5 = 8/15 job/hr (8/15 j/h)(1 h) = 8/15 job done that leaves (15-8)/15 = 7/15 to do (1/5)job/hr * t = 7/15 job t = 35/15 hr for S to finish 35/15 hr * 60 min/hr = 140 min

**algebra**

3j(j^2-17j +70) =3j (j-10)(j-7)

**algebra**

9 r^2 - 30 r + 25 = 0 (3 r -5)(3r-5) = 0 r = 5/3 and 5/3 repeated, parabola just touches r axis

**algebra**

2(2a^2-5a+3) is 2(2a-3)(a-1)

**algebra**

64 z^2 - 1 That is the difference of two squares remember a^2-b^2 = (a-b)(a+b) so (8z-1)(8z+1)

**nobody knows**

Did you try to copy and paste? That does not work.

**physics**

Assuming that they are in series, 1.2 amps goes through each so current density = 1.2 /(pi d^2/4) for each

**calculus too hard**

Use Steve's solution if no typos in problem statement.

**calculus too hard**

I am still not sure it is right maybe dx/dt = k(a-t) ?? if so try x = c + p t - kt^2/2 then dx/dt = p -kt then p = ka and if c = 0 then dx/dt = 0 +ka -kt = k(a-t) so then x = ka t - k t^2/2

**typos?**

I think you might mean dx/dt = k(a-x) but what is c?

**Maths**

tan 60 = X1/1 tan 30 = X2/1 d = X2 - X1 v = d/t t in hours = 10 s /(3600 s/hour)

**math**

angles OBA and OCA are right angle BOC is 90-40 = 50 ABC =180 - 20 - 90 = 70 = ACB

**Maths**

1.12 p = 15,000

**Calculus 3**

No, because multiply by sqrt 14 which is |n|

**Calculus 3**

n = 3 i +2 j + k we want F dot n = |F| |n| cos angle but we are given that |F| cos angle is 3 z/sqrt14 so what is |n|? sqrt (9+4+1) = sqrt 14 ha, that helps :) so F dot n = 3 z so do the integral of 3 z over the surface

**Calculus 3**

http://tutorial.math.lamar.edu/Classes/CalcIII/SurfIntVectorField.aspx boundary in first quadrant means x from 0 to 2 and y from 0 to 3 (sketch that thing)

**math**

89/18 =4 + something 4 * 18 = 72 89 -72 = 17 left over

**Physics**

well, sure the tension does work, but the idea is that you do not have to get into the innards of this system because its kinetic energy is described by the (1/2)(m1+m1)v^2 and (1/2) I omega^2 and its potential energy by the m g h of the two objects. You could solve the whole ...

**sorry, read -1 not -3**

-3(-2) = +6

**MATH**

y = -1 x +42 slope = -1 = change in y/change in x if change in x - -1 then change in y /-2 = -1 so change in y = -1 (-2) = +2

**Physics**

max ke = max Pe = m g h h = r (1-cos 60) = r/2 so max (1/2) m v^2 = m g r/2 max v^2 = g r T = m g + m v^2/r T = m (g + g) = 2 m g = 2(.05)(10) T = 1 Newton

**physics**

4 *10 = 40*v v = 1

**Physics**

q = c v same q on each v1+v2 = 100 q/c1 +q/c2 = 100 q/4 + q/2 = 100 3 q/4 = 100 q =400/3 on each now same v on each and total charge=800/3 and total c = 6 v = q/c = 800/18 = 44.4 volts

**algebra**

let's see we need 5*5-1 in the middle something of form (5c ) ( 5) (5c-1) (c +5)NO that gives +24, we want - (5c+1)(c-5) = 5c^2 -24c -5 progress so (5c+d)(c-5d) = 5c^2 -24cd -5d^2 done

**physics**

Ac = g there = v^2/R = omega^2 R omega = 2 pi radians/24 hours =2 pi radians /(24*3600)seconds R is given so find omega^2 R

**Specialist Mathematics**

|x+y| two possibilities A: x+y B: -x-y = -(x+y) if A: x+y is maximum when both are + then x+y = |x|+|y| if B: -(x+y) has same absolute value as A etc

**History -**

I think I might have picked C because some of them are in South America and Asia and the Middle East.

**Linear Relations MATHS**

You are welcome

**Linear Relations MATHS**

That means 3/4 of the way along the line segment from A to B That means 3/4 in x and 3/4 in y in x -4 +(3/4)(6 - -4) = -4+ 3*10/4 = = -16/4 +30/4 = 14/4 = 3 1/2 in y 6 + (3/4)(-7-6) = 6- 13*3/4 = 24/4-39/4 = -15/4 = -3 3/4 so (3.5 , -3.75) In part B same deal but times 3, not ...

**Math**

36 = .6 p so p =36/.6 = 360/6 = 60

**math help**

does "cross product" or "vector product" ring a bell? the cross product of two vectors is perpendicular to both +i +j +k +2 +1 +1 +1 -1 +2 (2+1)i +(1-4)j + (-2-1)k = 3i -3j -3 k

**History - Help**

http://www.fsmitha.com/h2/ch14-4.htm

**History - Help**

You are welcome.

**History - Help**

Yes, see https://en.wikipedia.org/wiki/Westphalian_sovereignty

**Mathematics**

50 (30/25) = 2*30 = 60

**Social Studies**

Where should I start???? Load and unload ships, trucks, trains, and planes or in the case of ports at the mouth of rivers (New Orleans, Rotterdam), transfer cargo between river barges and seagoing ships. Builds and repair ships and port facilities. Do the paper work and number...

**math**

(0,5800) and (5,7420) (7420-5800)/5 = (y-5800)/(x-0)

**math**

Well I showed you that the first choice is NOT a solution to the equation. However It might not be the only one. Check them all.

**math**

Try each of them for example -52 = -5(10) - 4 -52 = -54 I do not think so check the others as well.

**Math**

You are welcome.

**Math**

L,w,h area = 2 Lw + 2 Lh + 2wh = 600 so Lw+Lh+wh = 300 but L = 3w so 3 w^2 + 4 w h = 300 now V = L w h = 3 w^2 h so h = V/3w^2 3 w^2 + 4 w(V/3w^2) = 300 4 V/3w = 300 - 3 w^2 (4/3)V = 300 w - 3 w^3 we want d(4/3)V /dw = 0 300 = 9 w^2 w = (10/3)sqrt 3 L = 10 sqrt 3 w L = 100 so...

**physics**

I agree but wonder about the straight line. There is not enough gravity to hold them down, but there is still a force toward the earth center so I think the departure path would curve.

**Math**

You never know who will be online. All you can do is post the question. There are a lot of math teachers who check in here.

**Math**

Yep, it's right :)

**calculus**

right triangle 3,4,5 or 60,80,100 x= 60 y = 80 z = hypotenuse = 100 dx/dt = 80 dy/dt = 100 z^2 = x^2+y^2 2 z dz = 2 x dx + 2 y dy z dz/dt = xdx/dt +y dy/dt 100 dz/dt =60*80+80*100 dz/dt = 6*8+80 dz/dt = 128 km/hr

**History**

Heavens! Look at a map. What is the biggest river in the now United States? Texas where the beef comes from for Richmond is west of the river. Remember that fleet coming up from the Gulf of Mexico ("Damn the torpedoes" :)

**another no way**

You try first. I already took the course.

**No way**

I do not see any attempt by you to do these problems. I already took this subject and do not need the practice. You try first. Also read what you typed.

**Math**

25-13 = 12 which is the sum of the two bases at the ends h is the height area of rectangle in the middle = 13 h x is base of one triangle (below the 10) so 12-x is the other(below the 15 (12-x)^2 + h^2 = 225 x^2+h^2 = 100 ---------------------subtract 144-24x = 125 x = 19/24 ...

**math**

(9/14)(35,000) =

**Math**

Yes but do the division 9/3 = 3 laps/min 30/6 = 5 laps/min 20/5 = 4 laps/min Mary does the most laps /min

**math**

s = 3d d + 3d = 116 4 d = 116 d = 29 so s = 87

**Math (please help!!)**

It is also the incenter B http://www.google.com/search?q=incenter+of+triangle&ie=utf-8&oe=utf-8 and point of concurrency C http://www.google.com/search?q=iconcurrency+of+perpendicular+bisectors&ie=utf-8&oe=utf-8 and D

**30 to what ?**

30deg to horizontal or vertical? In either case, use Snell's law.

**math**

5 per year 5*20 = 100 twenty years

**history**

Clove production, slaves See: www.blackpast.org › Geography: Global African › Africa › KenyaSeyyid Said, also known as Said ibn Sultan, was a resourceful and energetic sultan ... moved the capital from Arabia to Zanzibar in order to initiate clove production...

**Social Studies**

push --> potato famine and nasty bosses drive people out pull ---> jobs and land draw those people as immigrants to Ellis Island.

**calcululs help me**

4x^2+8xy+9y^2-8x-24y+4=0 8xdx+8xdy+8ydx+18ydy-8dx-24dy=0 (8x+18y-24)dy= -(8x+8y-8)dx dy/dx = (-4x-4y+4)/(4x+9y-12)agree numerator = 0 when x+y=1 yes find d/dx(dy/dx)of (-4x-4y+4)/(4x+9y-12) = [(4x+9y-12)(-4dx-4dy)-(-4x-4y+4)(4dx+9dy)]/dx[(4x+9y-12)]^2 =4[(4x+9y-12)(-dx-dy)+(+...

**chemistry**

ZnO + 2HCl ---> ZnCl2 + H2O By the way H2O is ...... Zn = 65 g/mol O = 16 g/mol H = 1 g/mol Cl =35.5 g/mol 13.64 g ZnCl2 * 1 mol/(65+71)g = mols of ZnCl2 now you should be able to continue.

**American History**

I think A) http://millercenter.org/president/biography/monroe-foreign-affairs

**error !**

I multiplied by distance not time average speed = v/2 distance = .25 = t (v/2) t = .5/v then 3 v = 20 *.5/v 3 v^2 =10 v^2 = 10/3 v = sqrt(10/3) ================== check 3 v = 20 * t 3 sqrt (10/3)= 20 * .5/sqrt(10/3) 3 (10/3) = 20 * .5 yes

**physics**

change in momentum = force * time 3 v = 20*.25

**algebra 2**

ticket price p = 231/n p-4.5 = 231/(n+3) 231/n - 4.5 = 231/(n+3) 231(n+3)-4.5(n^2+3n) = 231 n 231*3 -4.5 n^2 - 13.5n = 0 4.5 n^2 + 13.5 n - 693 = 0 n = 11 or -14 so 11 =========================== check 231/11 = 21 231/14 = 16.5 yes, diff = 4.50

**Physics**

In other words unless there was energy input from a explosion on impact or something, no way the big block took off at 4.0 m/s

**Physics**

huh? .5*5 *2.9^2+.5*10*2.1^2 = 43.1 Joules .5*5 *0.9^2 + .5*10* 4^2 = 81.1 81.1-43.1 = 38 Joules more Something exploded :)

**American History**

ah come on !!!!

**calculus**

I assume you mean x^2 - x y - y^2 = 5 2 x dx - x dy -y dx - 2 y dy = 0 (2y-x)dy = (2x-y)dx dy/dx = (2x-y)/(2y-x) slope is undefined (vertical) when 2y-x = 0 or x = 2y so x^2 - x y - y^2 = 5 4y^2 -2y^2-y^2 = 5 y = +/-sqrt 5 then x = +/- 2 sqrt 5

**calculus**

surface area in m^2/radius in meters is meters radians is arc, no units so meters per radian

**algebra**

If any one of those three factors is zero, then the product is zero so z = 0 works z-1 = 0 works so z = 1 works z+3 = 0 works so z = -3 works therefore z = 0 or 1 or -3

**Algebra 1- Urgent**

In your table in part B the ratio is for example 10406.04/10303.01 = 1.01 check: 10303.01/10201 = 1.01 sure enough so that is increasing by ONLY ONE percent per year

**I do not believe you**

I think you have a very fundamental typo. We are talking about a constant rate of inflation here I bet you mean f(x) = 0.69 (1.03)^x in other words TO THE POWER x that would be 0.69 when x = 0 years, now 0.69 * 1.03 after one year 0.69 * 1.03 *1.03 after two years 0.69 *1.03*1...

**Algebra 1- Help please**

option 1 is not linear because it does not change by the same amount every year. It does not have a constant slope. option 2 increases by 100 per year, constant slope, straight line, linear ----------------------- a = A y^n 1100 =A y 1210 = Ay^2 1331 = A y^3 --------------- ...

**SS, PLZ HELP ME FAST!!!!**

hint: Japanese eat a lot more fish than people on the great plains eat.

**Calculus!! HELP!!**

1) The sides of the triangle shown increase in such a way that (dz/dt=1) and (dx/dt=(3dy/dx)) At the instant when x = 12 and y = 5, what is the value of dx/dt? ========================= You do not say but I suspect this is a 5,12,13 right triangle. If I am guessing right about...

**Maths**

I do not know what using rotational axis means but this is an ellipse 4(x^2-2x) +9(y^2+6y) = -4 complete squares 4(x^2-2x+1)-4+9(y^2+6y+9)-81=-4 4(x-1)^2 +9(x+3)^2 = 81 (x-1)^2/4.5^2 + (x+3)^2/3^2 = 1 ellipse

**Math**

area = (1/2)12*5 = 30 hypotenuse BC = 13 the area = 30 = (1/2)13*AD AD =60/13

**Math**

120,000/50 = 240,000/100 = 2400

**Probability and distribution**

16 total to start I could draw a white, then blue 6/16 * 7/15 or I could draw a blue, then white 7/16 * 6/15 add them 2(42/240) = .35

**math**

Try then (a^9/2)^3 = a^27/ 8

**History homework question**

Oh, 20th Century Leaders :) Civil Disobedience.

**History homework question**

Hudson River school is paintings. I do not understand the second question.

**American history**

well, if only about in Americas (not India, Africa etc) Spain - get gold out, make Catholics France - get fur and fish out, make Catholics. Do not send many French people, just a few missionaries and trappers. England - make trading partners that grow food and ship masts and ...

**physics**

v = omega r 10 = omega(2) omega = 5 radians/second Ac = v^2/r = omega^2 r = 25*2 = 50 m/s^2 F = m a = .5 *50 = 25 N (not 25.5)

**is (-2x)^-3 3 root of -2x?**

(-2x)^-3 = 1/(-2x)^2 = 1/[-2x(-2x)(-2x)] = 1/[(-8)(x^3)] =-1/(8 x^3)

**Maths**

subtract area of inside circle from area of outside circle radius inside = 28/2 = 14 radius outside = 14+3.5 = 17.5 so pi(17.5^2-14^2)

**Huh**

Your minister of education has two brains and they are headed for somewhere else?

**Jong**

Hair?

**typo**

x = 1 and y = 1 at t = 0 y = .5 x + b 1 = .5 + b b = .5 y = .5 x + .5

**calc**

y = sin t + cos^2 t - sin^2 t dy/dt = cos t -2cost sint -2 sint cost at t = 0 dy/dt = 1 x = cos t +2 sin t cos t dx/dt = -sint -2sin^2t+2 cos^2t at t = 0 dx/dt = 2 dy/dt / dx/dt = 1/2 = slope x = 1 and y = 1 at t = 0 y = 1 x + b b = 0 y = x

**Math**

1/(x+h) - 1/x (x - x - h)/(x^2+xh) -h/(x^2+xh) divide by h -1/(x^2+xh) let h--->0 -1/x^2 sure enough

**linear programming problem**

the intersection with p max is of 5x+10y=560 and 50x+20y=1600 x = 12, y=50 and p = 3220 http://www.wolframalpha.com/widget/widgetPopup.jsp?p=v&id=1e692c6f72587b2cbd3e7be018fd8960&title=Linear%20Programming%20Calculator&theme=blue

**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?