Question

Factorise the following using appropriate identities.
$18a^2-50$

Answer 1

$18a^2-50=2(9a^2-25)$

=2\left [ (3a)^{2}-(5)^{2} \right ]$

We know appropriate identities $x^2-y^2=(x+y)(x-y)$

Here x=3a and y=5

$\therefore 2\left[\right(3a{)}^2-\left(5{)}^2\right]$

=$2(3a-5)(3a+5)$