Wednesday

April 23, 2014

April 23, 2014

Total # Posts: 16,213

**Linear Algebra**

x-4y=12 and y=1/4x-3 a. one b. two c. infinitely many d. none ------------------------- x - 4 y = 12 x - 4 y = 12 Once again both lines are the same, infinite solutions, a y for every x

**Linear Algebra**

y=4x+3 and y=4x+4 a. one b. two c. infinitely many d. none ------------------- Those two lines are PARALLEL. They never cross!! No solutions in Euclidean geometry (There are in other systems of geometry)

**Linear Algebra**

How many solutions does the system of equations have? 2x=-10y+6 and x+5y=3 a. one b. two c. infinitely many d. none ---------------- Those two lines are THE SAME For every x there is a y infinite solutions, no intersection.

**S.S (DAMON)**

I think so.

**S.S (DAMON)**

I think so. In number 4, certainly D is a factor but I think B more usual and important.

**S.S (DAMON)**

I think the rest are ok but Costa Rica has by far the most stable democracy.

**S.S (DAMON)**

2. NO !!!! B checking the rest 1 os ok

**science**

An example of a net force of zero could be a squeeze between your fingers. If you squeezed hard enough I suppose you could split the wood. However I would tend under reasonable conditions to agree with your answer. If it had said a rubber, I would have said you could stretch i...

**science**

You can add the magnitudes of forces if they are in the same direction. However watch out. You can not just add them if they are not in exactly the same direction.

**science**

If you have two 5 Newton forces pushing a block to the right, that is a total of 10 Newtons pushing to the right. There may also be a moment due to the forces, but that is not part of the question.

**Global Studies**

YIKES !!!!

**S.S (DAMON)**

I have to see what you think first. I will check after lunch.

**science one question**

The questions are overly simplistic. It is impossible to change velocity at constant speed without acceleration. Even if going around a circle at constant speed, you have centripetal acceleration. In other words if you change direction at constant speed you need acceleration a...

**science one question?**

You are welcome, hardly a challenge though. Inches are certainly not SI :)

**science one question?**

SI: meter , kilogram , second so meter is distance unit in SI system We used to call it the MKS system.

**Physical Science**

Visible light photons are not energetic enough to penetrate skin and flesh.

**math You have a typo**

6" = .5 ft 3" = 3/12 ft = .25 ft 13.25 * 12.5 = 165.625 typo somewhere :( I bet it is 11' s" by 12' 6" because that gives140.625

**Physics**

weight down = m g = 97*9.81 = 952 N friction up = 810 N net force down = 142 N 142 = 97 a a = 1.46 m/s^2 v = a t 3.7 = 1.46 t at bottom so t = 2.54 seconds d = (1/2) a t^2 d = .5 (1.46)(2.54)^2 d = 4.69 meters long

**Check my social studies(PLEASE)**

I am no expert on this subject but: 1. I think B 2. ? not sure 3. ? not sure 4. I think d 5. I think a 6. I think c 7. I think c 8. I think c 9. I think a 10. I think c Perfect, we agree on not a single question ! Nada !!!

**Plz help me.**

I am a naval architect and a little touchy on the subject of the scientific world forgetting about the ocean and its basic importance :)

**Plz help me.**

By the way, all of this seems to leave the world oceans out. They fix more CO2 out of the atmosphere than anything else with phytoplankton photosynthesis. http://en.wikipedia.org/wiki/PI_curve

**Plz help me.**

1. D yes agree 2. D yes agree 3. C I believe 4. I think A, disagree with you. I am not entirely sure that trees fixing CO2 out of the atmosphere is a comprehensive solution though, but it would help. It certainly hurts to cut forests down and burn them up filling the sky with ...

**Physic II**

Q = V C V = i R i = - dQ/dt so i R = Q/C -dQ/dt = Q/(RC) -dQ/Q = dt/(RC) -ln Q = - t/(RC) Q = k e^[- t/(RC) ] as we all knew when t = 0 Q = Qi so Q = Qi e^[-t/(RC)] when is Q = .55 Qi ?? .55 = e^[-t/(RC)] ln .55 = -.5978 = -t/(RC) so t = 0.5978 R C

**Physic II**

C = Q/Vc so Q = CVc = integral i dt so Vc = (1/C) int i dt Vc = 0 at start 25 = i R + Vc 25 = i R + (1/C) int i dt 0 = R di/dt + i/C di/dt = -i/(RC) di/i =-dt/(RC) ln i = -t/(RC) i = e^[-t/(RC)] when t = 0, Vc = 0 and i = V/R i = (V/R) e^[-t/(RC)] Remember from above Vc =(1/C)...

**College math**

area = pi r^2 = 16 pi = 50.26548246 m^2 approximately circumference = 2 pi r = 25.13274123 meters

**College math**

You are welcome :)

**College math**

c^2 = a^2 + b^2 the hypotenuse is always the longest side.

**Maths**

two yellow and 10 total 2/10 = 0.2 or 1/5

**I give up**

I tried this with algebra a day or two ago and was unable to find the lower limit. I suspect it is zero but was unable to prove it with algebra.

**math**

b = shoe price s = sock price 2 b + 4 s = 125 times 3 3 b + 5 s = 182 times 2 6 b + 12 s = 375 6 b + 10 s = 364 ----------------- subtract 2 s = 11 s = $5.50

**Science question, only 1**

Only water not present in oceans is available for living things to use. Almost all of the water on earth is salt water in oceans.

**Physics**

5*200 = 1,000 watts = 1 kw 1 * 8 = 8 kw hr 8 cents/kw h * 8 kw h = 64 cents every 8 hours

**physics**

y = A sin 2 pi f t y"=-A(2 pi f)^2sin 2pift = -(2 pi f)^2 y -k y = m y" - k y = - m (2 pi f)^2 y (2 pi f)^2 = k/m f = (1/2pi)sqrt(k/m) f = (1/2pi) sqrt (200/50) f = 1/pi = .3183098852 Hz call it 0.318 Hz

**Science check my answers**

Fresh water is scarce but we have oceans full of salt water. 2 is C I believe.

**science**

A chemical bond was broken in separating H2O into hydrogen and Oxygen. New chemical bonds were made between the 2 hydrogen atoms and between the two Oxygen atoms.

**science, pls explain this!**

Hydrogen and oxygen 2 H2O ----- > 2 H2 + O2 in other word 4 H+ ions gain an electron and combine to make 2 neutral hydrogen molecules 2 O ions lose 2 electrons each to become a neutral O2 molecule

**Algebra - Functions**

1811 - 1200 = 611 commission .05 * sales = 611 sales = $12,220

**Math**

P= N [ 1 - (1+r)^-n ] /r P = present value, what he pays N = payment amount r = interest rate/period n = number of payments here n = 120 months need compound interest rate per month, not quarterly .045/4 = .01125 1.01125^4 = 1.045765 per year (1+r)^12 = 1.045765 (1+r) = 1.0037...

**math**

(1/30)hour/entry * 630 entries = 21 hours 21 hours * $7.50/hour = $157.50 They are not paying her enough.

**Alegbra**

(2x+3)(x+2) = (2 x^2 + 7 x + 6) now use distributive property to multiply that by (x-3) x (2 x^2 + 7 x + 6) = 2 x^3 + 7 x^2 + 6 x -3(2 x^2 + 7 x + 6) =-6 x^2 -21 x -18 add and get sum = 2 x^3 + x^2 -15 x -18

**Pre Algebra**

10/51.3 = .1949 .1949/8 = .024366

**Alegbra**

area= (2x+6)(3x-2) - (3x-4)(x+3) = 6 x^2 + 14 x -12 -[ 3x^2 +5 x -12 ] = 3 x^2 + 9 x You did not say what x is so cost = 4.75(x)(3x+9) = 14.25 (x)(x+3)

**Algebra ll**

You are welcome, good luck :)

**Algebra ll**

sum of logs is log of product log3 (4 x^2 + 7 x -2) = 5 base ^logbase(z) = z so 3^[log3 (4 x^2 + 7 x -2)] = 3^5 or (4 x^2 + 7 x -2) = 243 4 x^2 + 7 x - 245 = 0 (x-7)( 4x+35) = 0 x = 7 or x = -35/4

**a**

The side is (2x+3)? then the area is: (2x+3)(2x+3) = 4 x^2 + 12 x + 9 if x = 6 then Area = 4(36)+12(6)+9 = 144 + 72 + 9 = 225, too big :(

**Alegbra**

9.3*10^7 3.4 * 10^-7

**business math**

to reduce by 12 % multiply by 1-.12 = 0.88

**S.S**

Did you indeed Google to find out why Napoleon was willing to sell the gigantic Louisiana territory to Thomas Jefferson?

**S.S**

Google Louisiana Purchase

**physics**

- (3000)(891) Joules

**Chemistry**

Sulfur chlorate I suppose

**Physics**

Do it all over very carefully is all I can suggest.

**Physics**

CHECK MY ARITHMETIC !!! It came out awful coincidental though.

**Physics**

initial momentum = m V1 + 3m V2 final momentum = 4 m V3 same final momentum as initial so V3 = (V1+3 V2)/4 initial Ke = .5 m( V1^2 + 3 V2^2) final Ke = .5 (4m) (V3^2) = 2 m(V3^2) = 4 (.5m)V3^2 so change = .5m (V1^2+3V2^2 - 4 V3^2) but V3^2 = (V1^2 + 6V1V2 + 9V2^2)/16 4 V3^2 = ...

**math**

9 kilometers in 60 minutes = 9 kilometers/ hour

**Science asap**

1) B 2) condense = vapor to liquid evaporate = liquid to vapor both phase changes to precipitate is just to fall, not to change state.

**Science asap**

three states: ice , water , gas(water vapor) which has two of them ?

**Physics**

ok, that is may angle A so plug sin 59.2 and cos 59.2 in but check my algebra first

**Physics algebra error**

T = m(9.81)/cos A T sin A = m Ac = m v^2/R where R = 18 sin A so m (9.81) sin A/cosA = m v^2 /(18 sin A) v^2 = 9.81 * 18 * sin^2 A/cos A check my arithmetic !!!

**Physics**

I do not know where your angle is If from straight down then: T = tension m g = weight A = angle from vertical vertical equation T cos A = m g = m(9.81) so T = m(9.81)/cos A T sin A = m Ac = m v^2/R where R = 18 sin A so m (9.81) sin A = m v^2 /(18 sin A) v^2 = 9.81 * 18 * sin...

**Chemistry**

although what Steve said is fine.

**Chemistry**

Ferrous Nitrate (Iron+2) Fe(NO3)2 Ferric Nitrate (Iron +3) Fe(NO3)3

**English**

I suppose he could be any of us and what is he supposed to do about it anyway? It is those around him who reveal themselves ;) ( I am a physicist, not an English teacher, so you should ignore what I say )

**Physics**

71 kg = volume displaced * 1000 kg/m^3 so V = 71/1000 m^3 area * delta h = volume = 71/1000 2.34 * delta h = 71/1000 delta h = 30.34 /1000 in meters = 30.34/10 in cm = 3.03 cm

**help with math!!!!**

You should be able to do them yourself now.

**help with math!!!!**

Do not do it the way I did it. Use substitution, but you should get the same answer.

**help with math!!!!**

13. -x + y = -13 3x - y = 19 --------------- too easy to add them 2 x + 0 = 6 x = 3 y = -10

**help with math!!!!**

13. -x + y = -13 3x - 1 = 19 Is that a typo? No y in second equation? That sure makes it easy. 15. y = (7 x + 5) x - 3(7x+5) = 5 x - 21 x - 15 = 5 -20 x = 20 x = -1 y = -2 17. y = (-3x - 13) -2x + 5 (-3x-13) = -54 or 2x + 5 (3x+13) = 54 17 x + 65 = 54 17 x = - 11 x = -11/17 y ...

**Geometry**

by similar triangles divide hypotenuse into x and 29-x x/10 = 10/(29-x) 100 = 29 x - x^2 x^2 -29 x + 100 = 0 (x-25)(x-4) = 0 so the little triangle has short arm 4 and the big one has long arm 25 sqrt (100 + 16) = sqrt(116) = 2 sqrt(29) sqrt (100+625) = sqrt(725) = 5 sqrt(29) ...

**physics**

momentum = 3 (2) + 18 (0) = 6 before and after so 6 = 3 (u) + 18(v) or 2 = u + 6 v so u = (2 - 6 v) = 2 (1-3v) Ke same before and after: so 3(2^2) = 3u^2 + 18v^2 12 = 3(4)(1-3v)^2 + 18 v^2 2 = 2 (1 - 6v +9 v^2 ) + 3 v^2 0 = -12 v +18 v^2 + 3 v^2 21 v^2 = 12 v 21 v = 12 v = 12/...

**Science 6th grade Earth's day and night ANSWERS**

By the way, many would consider volcano eruptions destructive but for example they constructed the Hawaiian Islands and many other island and mountain chains.

**Science 6th grade Earth's day and night ANSWERS**

I agree with the answers as well.

**help i have no idea!!!!!!**

I assume you mean Amelia and not the rest of our family. She was a woman in a field dominated by men. It was even a struggle getting to learn to fly for a woman then. She was the ultimate "tomboy". Her parents got divorced, her father died of cancer.

**6th grade math**

The median gives you sort of a middle where half are above and half below. Use the median because Zimbabwe, Canada, and the US are not representative. As you can see, Zimbabwe pulls the average way down but is really what is often called an "outlier".

**Math ( trig )**

bottom of wheel up 5 so height above wheel bottom = 40 distance below center = 47 -40 cos A = 7/47 A = 81.4 degrees

**social studies(updated answers)**

I do not agree with your answers.

**S.S redo**

By the way, Google Vancouver Island and Fraser River gold rush.

**S.S redo**

Well, I agree with 10 and 12. 8 I am not Canadian, but did they not grow grain there? 9 is missing cod fish so I guess I would settle for water and wood. 11 read that again. You can not be serious.

**S.S redo**

1d 2c 3b 4a 5b 6b 7c I agree with those.

**computers**

If I replace 1/5 every year that is 100/5 = 20%

**Science**

No, if you decease the area then the force per unit area, called "the pressure", goes UP.

**Math ~ Check Answers ~**

I did not read it carefully.

**Whoa ! No**

23/92 = .25 .25^3 = .015625 .015625 * 240 = 3.75 ft^3

**Math ~ Check Answers ~**

yes, 60 was correct

**Math ~ Check Answers ~**

If it is similar, then ALL the dimensions, not just the height, are doubled. If you double lengths, you quadruple areas A = k L^2 90 * 4 = 360 in^2

**MATH**

x^2 - 4 x - 8 = 0 x = [ 4 +/- sqrt (16+32) ]/2 x = [ 4 +/- 4 sqrt 3 ] /2 x = 2 [1+/- sqrt 3 ]

**its my first day here in JISKHA QUESTION**

When I scroll down I see two questions of yours with replies.

**HELP JUST GIVE ME THE ANSWER A,B ,C, OR D**

Having made a living as a lobster fisherman at one point in my life, territory is everything.

**Physics**

force = change in momentum/time = m a if m constant Force * time = change in momentum F * 5 = 1400 * 25 F = 1400 * 5 = 7000 Newtons

**Physics**

1) true if stopped 2) yes max Ke at min height 3) Huh? It is true the normal force does not do work, but the friction force does so mechanical energy is LOST to heat. That is why it ends up lower and has to be towed back up to the start. 4) Well, this is true only if you defin...

**Physics**

- 3000 (719) Joules

**math/algebra**

This was actually just like the last one. It is your turn to do them now. I already passed the course.

**math/algebra**

x+z = 1 so z = (1-x) 2 x + 1 y = 1.5 so y = (1.5 - 2x) x + y + z = 0.5 so x + (1.5-2x) + (1-x) = 0.5 x + 1.5 - 2x +1 - x = 0.5 -2 x + 2.5 = 0.5 2 x = 2 x = 1 etc

**math/algebra**

z = (2-x) y = (3-x) x -(3-x) +(2-x) = 1 x - 3 + x + 2 - x = 1 x - 1 = 1 x = 2 z = 0 y = 1

**Math**

You are welcome :)

**Math**

20 k = 1980 k = 99 yes correct

**math**

2 x^2 -2 = 0 2 (x^2-1) = 0 (x-1)(x+1) = 0 x = 1 or x = -1

**liberal arts math**

(4x+1)^2 = 4x(4x+1) + 1(4x+1) =16 x^2 + 4x + 4 x + 1 = 16 x^2 + 8 x +1 or do FOIL if you know it. so: - x^2 + 3 = 16 x^2 + 8 x + 1 17 x^2 + 8 x - 2 = 0

**maths**

L w = 414 L = w+1 so w (w+1) = 414 w^2 + w = 414 w^2 + w - 414 = 0 w = [ -1 +/- sqrt(1+1656) ]/2 w = [ -1 +/- 40.706 ]/2 w = 19.9

**physic**

.5 = .9*n log .5 = n log .9 n = log .5 / log .9

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