Factorisation (Leaving Cert Mathematics): Revision Notes

Manipulation of Formulae

In many cases, algebraic terms in a formula may need to be moved around and rearranged meaning we have to manipulate the entire formula.

Consider the following formula that derives the area of a trapezoid :

Where $a$ is the length of the top of the trapezoid, $h$ is the vertical height and $b$ is the base.

We say $A$ is the subject of the formula. In a way, the formula is made in mind of finding the area. Another way of phrasing it is the $A$ is in terms of $a,b$ and $h$. That is, $A$ is on one side, and everything else is on the other.

But what if want to find $h$ given $A,a,b$. This would mean that we would have to put $h$ in terms of $A,a,b$, which make $h$ the subject of the formula. We can manipulate.

Example

Example