Question

factorise a2+1/a2-18​

Answer 1

Answer:

a2+1/a2-18

a2+1/a2=18

(a-1/a)^2+2.a.1/a=18

(a-1/a)^2=18-2

(a-1/a)^2=16

a-1/a=4

Step-by-step explanation:

Answer 2

Answer:

[a^2 + 1/a^2 -4][a^2+ 1/a^2 +4]

Step-by-step explanation:

a^2 + 1/a^2- 18

= a^2 + 1/a^2-2+2-18

= a^2 + 1/a^2- 2 -16

= [a + 1/a]^2 - 4^2                    ---using identity [a^2 -b^2]

= [a^2 + 1/a^2 -4][a^2+ 1/a^2 +4]