Question

已知A=3x+2y^2,B=x^2-2x-y^2,当|x+1|=2,|y-1|=3时,且x>o,y<o求A-B的值

Answer 1

当|x+1|=2,,
x+1=2或x+1=-2
x=1,或x=-3
|y-1|=3时
y-1=3或y-1=-3
y=4,或y=-2
且x>o,y<o
所以
x=1,y=-2
A-B=3x+2y^2-(x^2-2x-y^2)
=3x+2y^2-x^2+2x+y^2
=5x-x^2+3y^2
=5-1+3*4
=4+12
=16

Answer 2

A=3x+2y^2,B=x^2-2x-y^2
A-B=5x+3y^2-x^2
x>o,y<o
|x+1|=2,解得x=1
|y-1|=3，解得y=-2
代入得A-B=5x+3y^2-x^2=5+12-1=16

Answer 3

|x+1|=2，且x>o,所以x=1,
|y-1|=3，且y<o，所以y=-2，
A-B=x+y^2+x^2=1+4+1=6