Please help me out I really can’t afford failing this test

Answer:
I'm not really sure but I think it's 2
Step-by-step explanation:
So here's what I did;
x³+3x-9=x - 1 +2x
x³+3x - x -2x = 9 - 1
x³= 8
x = ³√8
x = 2
I hope this helps