(2X+1)²—(5X-4)²
=[2x+1-(5x-4)][2x+1+5x-4]
=(-3x+5)(7x+5)
16（X+y）²—9（x-y）²
=(4x+4y-3x+3y)(4x+4y+3x-3y)
=(x+7y)(7x+y)你确定都对么 亲？我们老师说错一题要罚5题 ~~~~(>_<)~~~~很确定