Question

当3x的二次方-x=1时,6x的三次方+7x的二次方-5x=? 要解释充分，有条有理！！！

还有，当3x的二次方-x=1时,6x的三次方+7x的二次方-5x+1994=?

Answer 1

3x^2-x=1

6x^3+7x^2-5x
=6x^3-2x^2+9x^2-5x
=2x(3x^2-x)+9x^2-5x
=2x+9x^2-5x
=9x^2-3x
=3(3x^2-1)
=3*1
=3

6x^3+7x^2-5x+1994
=3+1994
=1997