25（a-b）平方-16（a+b）平方

3个回答

=[5(a-b)]²-[4(a+b)]²
=(5a-5b)²-(4a+4b)²
=[(5a-5b)+(4a+4b)][(5a-5b)-(4a+4b)]
=(9a-b)(a-9b)