化简2（2X-7Y)(7Y+2X)+X^2-(-4X+5Y)(-5Y-4X)

分类: 作业答案 • 2021-12-20 01:29:09

问题描述：

答

=2(14XY+4X-49Y^2-14XY)+X^2-(20XY+16X^2-25Y^2-20XY)
=28XY+8X-98Y^2-28XY+X^2-20XY-16X^2+25Y^2-20XY
=-40XY+8X-73Y^2-15X^2

答

2（2X-7Y)(7Y+2X)+X^2-(-4X+5Y)(-5Y-4X)
=2（4X^2-49Y^2)+X^2-(16X^2-25Y^2)
=8X^2-98Y^2+X^2-16X^2+25Y^2
=-7X^2-73Y^2