[shantz]

I've got a problem that I need to solve for an unknown variable. I am given 2 multiple choice answers, and can't seem to get either answer. I've tried working backwards as well as can't come back to the original equation... Anyone able to help me out?

here is the equation:

i= AB / Ar+R

Solve for A:

the two answers provided are;

1) A = (-iR) / ir+B

2) A = ir / B-iR

I've been scratching my head for over an hour...

[Nlkko]

2.

Is this a troll post?

[Gh0stRider]

math :fuckthatshit:

[Gumby]

The challenge is that "A" appears twice in that equation... I'm stumped too.

[noventa]

looks likes it was suppose to be one, but something is weird, hold up. let me work it out

[noventa]

...

[noventa]

i=AB/(Ar+R)
i(Ar+R)=AB
Ari+Ri=AB
ARi-AB=-Ri
A(Ri-B)=-Ri
A=-Ri/(Ri-B)

[Gumby]

^
Ahhh that's right... embarrassed I didn't think of moving Ari & AB to one side so that I can factor A out.

[noventa]

one time in Calculus One long ago I remember getting screwed over by a question like that. After that, I never forgot that technqiue every again, haha.

[noventa]

2

[Oleophobic]

lol didn't notice the two different Rs....
yeah the answer doesn't match up with any of the choices

[Excelsis]

it's 50/50

just guess :fuckthatshit:
Posted via RS Mobile (http://www.revscene.net/forums/announcement.php?a=228)

[noventa]

yeah looks like even if you factor it out the negative, the numerator changes sign which is incorrect.

[shantz]

i = AB/Ar+R

multiply both sides by Ar+R

i(Ar+R) = AB

expand...

iAr + iR = AB

subtract iR from both sides

iAr = AB - iR

now subtract the AB from both sides

-AB + iAr = -iR

isolate the A

A(-B + ir) = -iR

divide both sides by (-B + ir)

A = -iR/(-B+ir)

factor out the negative

A = -1 iR / -1 (B-ir)

and since -1/-1 = 1

A = iR / (B-ir)


Thanks for all the help.

[noventa]

NP, math is fun!!

[buddy]

2)

[crazyazn]

Should've asked Yahoo!

[blee123]

bet you 80% of revscene user's facial expression is this (:heckno: )when reading that equation

[sindragon]

bet you 80% of revscene user's facial expression is this (:heckno: )when reading that equation

na we used this :fuckthatshit:

[blee123]

na we used this :fuckthatshit:

its this :heckno: then this :fuckthatshit: