16x^2-16x^3-4xy^2
=4X(4X-4X²-Y²)
是不是题目错了,应该是
16x^2Y-16x^3-4xy^2
=4X(4XY-4X²-Y²)
=-4X(4X²-4XY+Y²)
=-4X(2X-Y)²