25(a-b)的平方-64(2a+b)的平方
=[5(a-b)-8(2a+b)][5(a-b)+8(2a+b)]
=(5a-5b-16a-8b)(5a-5b+16a+8b)
=(-11a-13b)(21a+3b)
=-3(11a+13b)(7a+b)