# I think this is simple but I just cant work out how!

1. Apr 28, 2010

### oliver.smith8

how does $$\frac{1/a -1/b}{1/a+1/b}= \frac{b-a}{b+a}$$

Ive been trying to work this out for ages

thanks

2. Apr 28, 2010

### Tac-Tics

It's simple algebra. Here's a few hints.

The right hand side, as given, is this:

$$\frac{\frac{1}{a} - \frac{1}{b}}{\frac{1}{a} + \frac{1}{b}}$$

But this can be written more clearly as:

$$(\frac{1}{a} - \frac{1}{b})(\frac{1}{a} + \frac{1}{b})^{-1}$$

From there, apply algebraic operations to this expression until it equals the right hand side.

3. Apr 28, 2010

### Gigasoft

Think about what value you need to multiply the left hand side with to make it equal the right hand side.

4. Apr 28, 2010

### elect_eng

Multiply by ab in both the numerator and the denominator. This is multiplying by one.

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