(1)(x^2-2)^2-4x^2
={(x^2-2)+2x}{(x^2-2)-2x}
=(x^2+2x-2)(x^2-2x-2)
(2)(2x^2+1)^2-4x^2
={(2x^2+1)+2x}{(2x^2+1)-2x}
=(2x^2+2x+1)(2x^2-2x+1)
(3)(x^2+y^2)^2-9x^2y^2
={(x^2+y^2)+3xy}{(x^2+y^2)-3xy}
=(x^2+3xy+y^2)(x^2-3xy+y^2)
(4)(x^2+3y^2)^2-x^2y^2
={(x^2+3y^2)+xy}{(x^2+3y^2)-xy}
=(x^2+xy+3y^2)(x^2-xy+3y^2)
答え間違ってたらすみません💦