Hello dtay

Welcome to Math Help Forum!You need to create two equations involving and , and then eliminate to find an equation involving just and .

Here are some clues:

The first statement can be written:

So if we multiply by

(1)

Now write down the second statement in a similar way, and use equation (1) to eliminate .

Then re-arrange so that you have on one side, and on the other. Finally, divide both sides by to find . I get the answer:

Can you fill in the gaps?

Grandad