化简求值：【（x+2y)²-(x+y)(3x-y)-5y²]/2x,其中x=-2,y=二分之一详细过程跪求!

题目

化简求值：【（x+2y)²-(x+y)(3x-y)-5y²]/2x,其中x=-2,y=二分之一详细过程跪求!

答案

[(x+2y)²-(x+y)(3x-y)-5y²]/2x,
=(x²+4xy+4y²-3x²-3xy+xy+y²-5y²)÷2x
=(-2x²+2xy)÷2x
=-x+y
=-(-2)+1/2
=2+1/2
=5/2