1/s+1/i=1/f, need i = ...

[BearishSun]

Hello,

how do I get equation "1/s+1/i=1/f" in the form i = ... ?

The solution is i = f*s/(s-f), but I'd like to know the steps for getting the solution.

Thanks in advance

 

[galactus]

Find your LCD. It is \(\displaystyle sif\), isn't it?.

\(\displaystyle \frac{if}{if}\cdot\frac{1}{s}+\frac{sf}{sf}\cdot\frac{1}{i}=\frac{si}{si}\cdot\frac{1}{f}\)

Now that the denominators are the same, concentrate on the numerators.

\(\displaystyle if+sf=si\)

Now, solve for i.

 

[BearishSun]

So simple...still, I doubt it would occur to me

Thanks again

 

[Deleted member 4993]

Too many ifs in the problem .... :mrgreen: