Question

Factorise:
a^4 + 3a^2 - 4

Answer 1

a^4 + 3a^2 - 4

a^4 + a^2 + 4a^2 - 4

a^2 (a^2 + 1) - 4(a^2 +1)

(a^2 + 1)(a^2- 4)

Answer 2

let a^2 be some variable as x

so the eq. becomes x^2 + 3x - 4

so the factors will be:

(x+4) and (x-1)

x=1 or -4

a^2= 1 or -4

so a^2 cannot be negative

so α^2=1 is the answer