Question

已知|x-y-2|+x^+2xy+y的平方=0,求x+2y的值

Answer 1

∴|x-y-2|+(x²+2xy+y²)＝0

→|x-y-2|+(x+y)²＝0.

∴x-y-2＝0且x+y＝0,

∴x＝1,y＝-1.

∴x+2y＝1+2·(-1)＝-1.