化简求值答案(x³-2y³-3x²y)-[3(3x³-2y³)-4x²y] x=－2 y=－1请先化简,然后求值,

化简求值答案
(x³-2y³-3x²y)-[3(3x³-2y³)-4x²y] x=－2 y=－1
请先化简,然后求值,

(x³-2y³-3x²y)-[3(3x³-2y³)-4x²y]=
(x³-2y³-3x²y)-9x³+6y³+4x²y=
-8x³+4y³+x²y=
-8*(-2)³+4*(-1)³+（-2）² *（-1）=
64-4-2=
58

(x^3-2y^3-3x^2y)-[3(3x^3-2y^3)-4x^2y]=-8x^3-8y^3+x^2y=-8(x^3+y^3)+x^2y=-8[(-2)^3+(-1)^3]+(-2)^2x(-1)=72-4=68

(x3 -2y3-3x2y)-[3(3x3-2y3)-4x2y]
=x3-2y3-3x2y-9x3+6y3+4x2y
= -8x3+4y3+x2y
= -8*(-2)3+4*(-1)3+(-2)2*(-1)
=64-4-4
=56