1.
|x-2|与（y+1/2）²互为相反数
|x-2|+（y+1/2）²=0
x=2 y=-1/2
x²y-3xy²-1/3（3x²y-2 xy²）
=x²y-3xy²-3x²y+2 xy²/3
=-2x²y-7 xy²/3
=-2*2^2*(-1/2)-7*2*(-1/2)^2/3
=4-7/6
=17/6
2.
已知:A+B=3x^2-5x-1,A-C= - 2x+3x^2-5
两式相减B+C=3x²-5x-1+2x-3x²+5
=-3x+4
已知IxI=1/2
则x=1/2或-1/2
1.x=1/2时,B+C=-3*(1/2)+4=5/2
2.x=-1/2时,B+C=-3*(-1/2)+4=11/2