Question

a^4-5a^2+4
factorise ​

Answer 1

Answer:

(a+2)(a-2)(a+1)(a-1)

Step-by-step explanation:

a⁴-5a²+4 = (a²)² - 5a² + 4

Let k = a²

k² -5k + 4 = k² - k - 4k +4

= k(k-1) - 4(k-1)

= (k - 4)(k - 1)

replace k by a²

= (a² - 4)(a² - 1)

= (a² - 2²)(a² - 1²)

= (a+2)(a-2)(a+1)(a-1)