化简求值:(x+2y)²-(x+y)(x-y),其中x=-2,y=二分之一

化简求值:(x+2y)²-(x+y)(x-y),其中x=-2,y=二分之一
化简求值:(x+2y)²-(x+y)(x-y),其中x=-2,y=二分之一

化简求值:(x+2y)²-(x+y)(x-y),其中x=-2,y=二分之一
(x+2y)²-(x+y)(x-y)
=x²+4xy+4y²-x²+y²
=4xy+5y²
=4x(-2)x(1/2)+5x(1/2)²
=-4+5/4
=-11/4

:(x+2y)²-(x+y)(x-y)
=x²+4xy+4y²-x²+y²
=4xy+5y²
=4×(-2)×½+5×¼
=-4+5/4
=-11/4