因式分解2题1.a的平方/25+b的平方/16-ab/102.9x的平方-[x-2y]的平方

a^2/25+b^2/16-ab/10
=（a/5-b/4)^2
2.
9x^2-[x-2y]^2
=(3x+x-2y)(3x-x+2y)
=(4x-2y)(2x+2y)
=4(2x-y)(x+y)