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(x+y)-5xy
=-3*6-5*4
=-18-20
=-38