9x+6x^2-3(x-2/3x^2),其中x=-3.先化简,再求值.急

问题描述:

9x+6x^2-3(x-2/3x^2),其中x=-3.先化简,再求值.

9x+6x^2-3(x-2/3x^2),
=9x+6x^2-3x+2x^2
=8x^2+6x
=8*9+6*(-3)
=72-18
=54

上面回答得很好
9X+ 6X^2 - 3(X - 2/3 X^2)
= 9X + 6X^2 -3X + 2X^2
= 6x + 8x^2
因为 X=-3
则:原式=-18 +72
= 54