先化简,再求值 5(x+y)(x-y)-2(x+y

先化简,再求值 5(x+y)(x-y)-2(x+y)的二次方-3(x-y)的二次方,其中x=3,y=-2 要过程!

1个回答

原式=5(x²-y²)-2(x²+2xy+y²)-3(x²-2xy+y²)
=5x²-5y²-2x²-4xy-2y²-3x²+6xy-3y²
=-10y²+2xy
=-40-12
=-52