(i) a4 – b4
Answer: a4-b4 = (a²+b²)(a²-b²)
(ii) p4 – 81
=(p²+9)(p²-9)
(iii) x4 – (y + z)4
Answer: x4 – (y + z)4
= (x²+(y+z) ²)(x²-(y+z) ²)
= (x²+(y+z)²)[(x+y+z)(x-y-z)]
(iv) x4 – (x – z)4
Answer: x4 – (x – z)4
=(x²-(x-z) ²)(x²+(x-z) ²)
=[(x+x-z)(x-x+z)](x²+(x-z) ²]
(v) a4 – 2a²b² + b4
Answer: a4 – 2a2b2 + b4
This can be factorised by using the identity; (a - b)2 = a2 – 2ab + b2
Factors = (a2 – b2)2 = (a2 – b2)(a2 – b2)
