因式分解：(1)-18m^4+9m^2n^2+5^4,(2)x^4-10x^2y^2+9y^4

题目

因式分解：(1)-18m^4+9m^2n^2+5^4,(2)x^4-10x^2y^2+9y^4

答案

(1)-18m^4+9m^2n^2+5n^4
=-(18m^4-9m^2n^2-5n^4)
=-(3m^2+n^2)(6m^2-5n^2)
(2)x^4-10x^2y^2+9y^4
=(x^2-y^2)(x^2-9y^2)
=(x+y)(x-y)(x+3y)(x-3y)