化简:(3x+1)+2(x^2+2x-1)-3x^2,其中x=3.
问题描述:
化简:(3x+1)+2(x^2+2x-1)-3x^2,其中x=3.
答
(3x+1)+2(x^2+2x-1)-3x^2
=3x+1+2x^2+4x-2-3x^2
=7x-x^2-1
当x=3时
7x-x^2-1
=21-9-1
=11