Question

1. (y²-2a)(2a+y²)
2. (3x²+x)²
3. (2+m)²(2-m)²

Answer 1

$1.~ (y^2-2a)(2a+y^2)=(y^2-2a)(y^2+2a)=(y^2)^2-(2a)^2=y^4-4a^2$

$2.~(3x^2+x)^2=9x^4+6x^3+x^2\\ 3.~(2+m)^2(2-m)^2=((2+m)(2-m))^2=(4-m^2)^2=16-8m^2+m^4$