(5)先化简,再求值:3x2y-[2x2y-(2xy-3x2y)]+3xy2,其中x=3,y=-1/3
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(5)先化简,再求值:3x2y-[2x2y-(2xy-3x2y)]+3xy2,其中x=3,y=-1/3
(5)先化简,再求值:3x2y-[2x2y-(2xy-3x2y)]+3xy2,其中x=3,y=1/3
(5)先化简,再求值:3x2y-[2x2y-(2xy-3x2y)]+3xy2,其中x=3,y=1/3
3x^2y-[2x^2y-(2xy-3x^2y)]+3xy^2
=3x^2y-[2x^2y-2xy+3x^2y]+3xy^2
=3x^2y-5x^2y+2xy+3xy^2
=-2x^2y+2xy+3xy^2
=-2*3^2*(-1/3)+2*3*(-1/3)+3*3*(-1/3)^2
=6-2+1
=5
=3x^2y-[2x^2y-2xy+3x^2y]+3xy^2
=3x^2y-5x^2y+2xy+3xy^2
=-2x^2y+2xy+3xy^2
=-2*3^2*(-1/3)+2*3*(-1/3)+3*3*(-1/3)^2
=6-2+1
=5
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