Rearranging Formulae

1. Rearranging Formulae

2. Things to remember: • Don’t rush it. You must go through each stage of your method and not try to skip any. • If you are making x the subject it means that you want to end up with x= and this is the only x in your answer. • Whatever you do to one side of the equals sign you must do to the other.

3. a = x + x = Example Rearrange the formula a = x + .to make x the subject. Method - ad = dx + cx multiply both sides by d dx + cx = ad rearrange to get x’s on the left x(d + c) = ad factorise divide by (d + c)

4. a = + p = Example Rearrange the formula a = + .to make p the subject. Method - apq = q + p multiply both sides by pq apq – p = q rearrange to get p’s on the left p(aq – 1) = q factorise divide by (aq – 1)

5. Example Rearrange the formula a = b + .to make p the subject. Method - a = b + a(1 + p) = b(1 + p) + c multiply both sides by 1 + p a + ap = b + bp + c expand brackets ap – bp = b + c – a rearrange to get p’s on the left factorise p(a – b) = b + c – a divide by (a – b) p =

6. Example Rearrange the formula s = b + .to make t the subject. Method - s = b + s – b = subtract b from both sides (s – b)² = square both sides = (s – b)² rearrange to get t on the left multiply by p t = p(s – b)²