(3x-y)²-(2x+y)²-5x(x-y),其中x=3,y=1

问题描述:

(3x-y)²-(2x+y)²-5x(x-y),其中x=3,y=1

(3x-y)²-(2x+y)²-5x(x-y)
=9x²-6xy+y²-4x²-4xy-y²-5x²+5xy
=(9x²-4x²-5x²)+(5xy-6xy-4xy)+(y²-y²)
=-5xy
=-5x3x1
=-15