已知X+Y=6,XY=-4,求(5X-4Y-3XY)-(8X-Y+2XY)的值
问题描述:
已知X+Y=6,XY=-4,求(5X-4Y-3XY)-(8X-Y+2XY)的值
答
(5X-4Y-3XY)-(8X-Y+2XY)
=-(3X+3Y)-5XY=-3*6+4*5=2