已知x-2y=3,则1/2x²-2xy+2y²的值是

问题描述:

已知x-2y=3,则1/2x²-2xy+2y²的值是

1/2x²-2xy+2y²
=1/2(x²-4xy+4y²)
=1/2(x-2y)²
=1/2*3²
=9/2