Question

A=-3x+2y的平方,B=x的平方-2x-y的平方,x+2的绝对值+(y-1)平方=0,求A-B

Answer 1

|x+2|+(y-1)²=0

绝对值项与平方项均恒非负,两者之和=0,两者分别=0

x+2=0 x=-2

y-1=0 y=1

A-B

=-3x+2y²-(x²-2x-y²)

=-x²-x+3y²

=-(-2)²-(-2)+3×1²

=-4+2+3

=1