已知x2+x-3=0,那么(3-x2-x3)/(x-1)=?

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已知x2+x-3=0,那么(3-x2-x3)/(x-1)=?

已知x2+x-3=0,那么(3-x2-x3)/(x-1)=?
已知x2+x-3=0,那么(3-x2-x3)/(x-1)=?

已知x2+x-3=0,那么(3-x2-x3)/(x-1)=?
由x^2+x-3=0,
得x^3+x^2=3x,
代入
(3-x2-x3)/(x-1)
=(3-3x)/(x-1)
=-3

x²=3-x
x³=3x-x²=3x-(3-x)=4x-3
所以
(3-x²-x³)/(x-1)
=(3-(3-x)-(4x-3))/(x-1)
=(3-3+x-4x+3)/(x-1)
=(3-3x)/(x-1)
=-3

因为x2+x-3=0,所以x2+x=3,所以3-x2-x3=3-x(x+x2)=3-x*3=3-3x=-3(x-1),所以(3-x2-x3)/(x-1)=-3(x-1)/(x-1)=-3.