4(a+b)的平方-9（a-b）的平方=[2(a+b)]²-[3(a-b)]²=[2(a+b)+3(a-b)][2(a+b)-3(a-b)]=(5a-b)(5b-a)25x²-1/(16y²)=(5x)²-[1/(4y)]²=(5x+1/4y)(5x-1/4y)