Question

factorise this: a^2 + 1/a^2 -27

Answer 1

a²+1/a² -2 - 25

= (a - 1/a)² - 5²

=( a-1/a-5 )(a-1/a + 5)

Hope helped !

Answer 2

This is your answer,

As 27 is not a perfect square

so it is better to take -2-25

Now take (a^2+1/a^2-2)

see it is coming in the formula of

(a-b)^2=(a)^2-2ab+(b)^2