x²-2(xy-y²+1)+3(2/3xy-y²) (x-2)²+∣y+1∣=0 x=2 y=-1
=x²-2xy+2y²-2+xy-3y²
=x²-xy-y²-2
=2²-2*(-1)-(-1)²-2
=4+2-1-2
=3
2x²-3(-1/3x²+2/3xy-y²)-3x² x=2 y=-1
=2x²+x²-2xy+3y²-3x²
=3y²-2xy
=3*(-1)²-2*2*(-1)
=3+4=7
5x²+2xy-3(1/3xy+1)-4x²+xy x=-2 y=1/2
=5x²+2xy-xy-3-4x²+xy
=x²+2xy-3
=(-2)²+2*(-2)*1/2-3
=4-2-3
=-1
(-1)^4+∣-24∣x(5/4-7/6)
=1+24×5/4-24×7/6
=1+30-28
=3
-1^2015÷(-5)²×(-5/3)+∣0.8-1∣
=-1÷25×(-5/3)+0.2
=1/15+1/5
=1/15+3/15
=4/15
你啥意思？
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