Question

已知x^2-3x=1,则多项式3x^3-11x^2+3x+2的值等于？

＾是平方

Answer 1

解：因x^2-3x=1 所以 x^2-3x-1=0
则 原式＝3x^3-9x^2-3x-2x^2+6x+2
＝3(x^2-3x-1)-2(x^2-3x-1)
=0+0
=0

Answer 2

3x^3-11x^2+3x+2
=3x^3-9x^2-2x^2+3x+2
=3x(x^2-3x)-2x^2+3x+2
∵x^2-3x=1
∴原式=3x*1-2x^2+3x+2
=6x-2x^2+2
=-2(x^2-3x)+2
=-2*1+2
=-2+1
=-1

Answer 3

^是平方吗

Answer 4

3x^3-11x^2+3x+2
=3x^3-9x^2-2x^2+6x-3x+2
=3x(x^2-3x)-2(x^2-3x)-3x+2
=3x-2-3x+2
=0

Answer 5

3x^3-11x^2+3x+2
＝3x（x^2－3x）-2x^2+3x+2
=-2x^2+6x+2
=-2(x^2－3x)+2
=-2+2
=0