1、=[4x+(7y-5)][4x-(7y-5)]=(4x)²-(7y-5)²=16x²-49y²+70y-252、=[(1/2a+2b)(1/2a-2b)] ²=(1/4a²-4b²)²=1/16a的4次方-2a²b²+16b的4次方