Question 307911
don't "factor."  Instead use synthetic division

3  1 2 -5 30
     3 15 30
   1 5 10 60

Are you sure the problem isn't x^3+2x^2-5x-30? And are you sure you're not dividing by x+3?

Because the problem you posted has a remainder of 60.  1x^2+5x+10 R 60

But if one of the signs is wrong in what you posted, then the final number would be -30 instead of positive 30 and would leave us with no remainder.