X+Y=-1,XY=3求5(XY+2Y)+(6X-(2XY+Y-3X))的值
问题描述:
X+Y=-1,XY=3求5(XY+2Y)+(6X-(2XY+Y-3X))的值
答
5(XY+2Y)+(6X-(2XY+Y-3X))
=5XY+10Y+(6X-2XY-Y+3X)
=5XY+10Y+6X-2XY-Y+3X
=(5XY-2XY)+(6X+3X)+(10Y-Y)
=3XY+9X+9Y
=3XY+9(X+Y)
=3*3+9*(-1)
=9-9
=0