先化簡,再求值:(xy-3x^2)-2(xy-2x^2-1),其中x、y滿足條件丨x+2丨+(y-1)^2=0

先化簡,再求值:(xy-3x^2)-2(xy-2x^2-1),其中x、y滿足條件丨x+2丨+(y-1)^2=0

丨x+2丨+(y-1)^2=0
丨x+2丨=0,(y-1)^2=0
x+2=0,y-1=0
x=-2,y=1
所以
(xy-3x^2)-2(xy-2x^2-1)
=(xy-3x^2)-2xy+4x^2+2
=-xy+x^2+2
=-(-2)×1+(-2)^2+2
=2+4+2
=8