若x=根号5-2,求x^3+4x^2-2x-2的值

若x=根号5-2,求x^3+4x^2-2x-2的值
若x=根号5-2,求x^3+4x^2-2x-2的值

若x=根号5-2,求x^3+4x^2-2x-2的值
x^3+4x^2-2x-2
=x^3+4x^2+4x-6x-2
=x(x^2+4x+4)-6x-2
=x(x+2)^2-6x-2
=x(√5-2+2)^2-6x-2
=5x-6x-2
=-x-2
=-(√5-2)-2
=-√5+2-2
=-√5