(i) `a^4 - b^4`
`(a^2)^2 - (b^2)^2`
`(a^2 - b^2)(a^2 + b^2)`
(ii) `p^4 - 81`
`(p^2)^2 - 9^2`
`(p^2- 9)(p^2 + 9)`
(iii) `x^4 - (y+z)^4`
`(x^2)^2- ((y+z)^2)^2`
`= (x^2 - (y+z)^2)(x^2 + (y+z)^2)`
(iv) `x^4 - (x-z)^4`
`(x^2)^2 - ((x-z)^2)^2`
`(x^2 - (x-z)^2)(x^2 + (x-z)^2)`
(v) `a^4 - 2a^2b^2 + b^4`
`(a^2)^2 - 2a^2b^2 + (b^2)^2`
`(a^2-b^2)^2`
answer