Question

factorise the following

Answer 1

$x^4+y^4-11x^2y^2 →x^4+y^4-11x^2y^2+9x^2y^2-9x^2y^2 →x^4+y^4-2x^2y^2-9x^2y^2 →x^4-x^2y^2-x^2y^2+y^4-[3xy]^2 →x^2[x^2-y^2]-y^2[x^2-y^2]-[3xy]^2 → [x^2-y^2]^2-[3xy]^2 use identity a^2-b^2=[a+b][a-b]$

u get as follows

[x²-y²+3xy] [x²-y²-3xy]