A)(x^4-x^2)^2=(x^4-x^2)*(x^4-x^2)=x^8-2x^6+x^4=x^4(x^4-2x^2-1) b) (y^4+y^3)^2=y^8+2y^7+y^6=y^6*(y^2+y+1) c) (6ab^2-a^2b)^2=36a^2b^4-12a^3b^3+a^4b^2=a^2b^2(36b^2-12ab+a^2) d) (5a^4-2a^2b^4)^2=25a^8-10a^2b^4+4a^4b^8