Question

multiply
(x^2+y^4)(x^2-y^4)

Answer 1

use the difference of squares rule

(x^2+y^4)(x^2-y^4) = (x^2)^2 - (y^4)^2

(x^2+y^4)(x^2-y^4) = x^(2*2) - y^(4*2)

(x^2+y^4)(x^2-y^4) = x^4 - y^8

Answer 2

thank you