Rearranging equations - help!

[birdman]

Hello all,

 

Hope someone can help with this simple problem I'm having rearranging this equation to put X in terms of Y:

 

Y = 2X / (1-4X)

 

Answer given is X = Y / (2+4Y) but I can't see why, can anyone help me out with the intermediate steps?

 

Many thanks!!

[Klaynos]

first 3 things to do are, multiply by any x terms which are divisions, multiply out any brackets, and then move all x terms to one side of the equation.

[birdman]

Hello Klaynos,

 

Thanks for the swift reply, but I'm a little confused by "multiply by any x terms which are divisions"?

[insane_alien]

see how there is a term with x in it that is a division(big hint: (1-4x)) start of by multiplying both sides by that. after you do that the whole thing should become much much easier.

[Klaynos]

well any term that has x in it that is on the bottom of the equation so if you had:

 

2y=10x/12-9x you would multiply by 12-9x giving you 2y(12-9x)=10x

[birdman]

Got it!

 

Y = 2X / (1-4X)

Y * (1-4X) = 2X

Y-4YX = 2X

Y = 2X+4YX

Y = X(2+4Y)

Y/(2+4Y) = X

 

Can't believe I didn't see that earlier, thanks for your help guys..

[insane_alien]

no problem. i had a feeling that that was the case. we all get like that from time to time. even my old math lecturer, in the middle of a lecture. it was part of something a bit more complicated than this but it was a really simple bit he got stuck on.