如果3x^3-x=1,求9x^4+12x^3-3x^2-7x+1
问题描述:
如果3x^3-x=1,求9x^4+12x^3-3x^2-7x+1
答
=9x^4+4(x+1)-3x^2-7x+1
=9x^4-3x^2-3x+5
=9x^4-3x(x+1)+5
=9x^4-3x×3x^3+5
=5