What do I do, I'm the HORRIBLE when it comes to math :'( I have a lot more of these but i need to learn how to do this.

1/a + 1/b = c for a

P= A/1+rt for r

I= kE/R for R

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- Mar 4th 2011, 09:29 AMmrmyers22Solve for the specified variable?
What do I do, I'm the HORRIBLE when it comes to math :'( I have a lot more of these but i need to learn how to do this.

1/a + 1/b = c for a

P= A/1+rt for r

I= kE/R for R - Mar 4th 2011, 10:00 AMQuacky
$\displaystyle \frac{1}{a}+\frac{1}{b}=c$

Start by removing the fractions (just multiply through by the denominators, as below):

$\displaystyle a(\frac{1}{a}+\frac{1}{b})=a\times c$

$\displaystyle 1+\frac{a}{b}=ac$

$\displaystyle b(1+\frac{a}{b})=ac\times b$

$\displaystyle b+a=abc$

Rearrange so that all terms involving 'a' are on one side of the equation:

$\displaystyle b=abc-a$

Factor out an $\displaystyle a$:

$\displaystyle b=a(bc-1)$

Divide through by the non-a factor:

$\displaystyle \frac{b}{bc-1}=a$

Try the others yourself, it's the same principle! Post your working if you're still unable to continue. - Mar 4th 2011, 10:56 AMWilmer