(4x^3-x^2+5)+(5x^2-x^3-4),其中x=-2 .(xy-2/3y-2/3)-(1/2x-1/2xy+1),其中x=2/3,y=3/4.
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(4x^3-x^2+5)+(5x^2-x^3-4),其中x=-2 .(xy-2/3y-2/3)-(1/2x-1/2xy+1),其中x=2/3,y=3/4.
(4x^3-x^2+5)+(5x^2-x^3-4),其中x=-2 .(xy-2/3y-2/3)-(1/2x-1/2xy+1),其中x=2/3,y=3/4.
(4x^3-x^2+5)+(5x^2-x^3-4),其中x=-2 .(xy-2/3y-2/3)-(1/2x-1/2xy+1),其中x=2/3,y=3/4.
(4x^3-x^2+5)+(5x^2-x^3-4)=3x^3+4x^2+1
当x=2时,带入原等式=3*2^3+4*2^2=3*8+4*4= 40;
(xy-2/3y-2/3)-(1/2x-1/2xy+1)=xy-2/3y-2/3-1/2x+1/2xy-1
=3/2xy-2/3y-1/2x-5/3
当x=2/3,y=3/4,代入原等式=3/2*2/3*3/4-2/3*3/4-1/2*2/3-5/3
=3/4-1/2-1/3-5/3
=-7/4
(4x^3-x^2+5)+(5x^2-x^3-4)=3x^3+4x^2+1=3×(-2)^3+4×(-2)^2+1=3×(-8)+4×4+1=-24+16+1=-7
??问题
(4x^3-x^2+5)+(5x^2-x^3-4)=3x^3+4x^2+1
当x=2时,带入原等式=3*2^3+4*2^2=3*8+4*4=40
(xy-2/3y-2/3)-(1/2x-1/2xy+1)
=xy-2/3y-2/3-1/2x+1/2xy-1
=3/2xy-2/3y-1/2x-5/3
当x=2/3,y=3/4,
原式=3/2*2/3*3/4-2/3*3/4-1/2*2/3-5/3
=3/4-1/2-1/3-5/3
=-7/4