Question

The rationalising factor for the number $3-7\sqrt{2}$ is ____

(1 mark)

Answer 1

We know that $(a+b)(a-b)=a^2-b^2$

The expression that is multiplied with an irrational expression to obtain a rational number is called the "rationalising factor".

Thus, to rationalise $(3-7\sqrt{2})$, we multiply it with $3+7\sqrt{2}$.

(1 mark)