First of all Horner First we try with -3 1. 2. -5. -6. -3. 3. 6 1. -1. -2. 0 To verify: -3^3+2*-3^2+15-6=0
Now we have this equation (X+3)*(x^2 - x -2)=0
I dont know If you know sum and product but that is the easiest way so sum= 1 product = 2 so 2 and -1 are the answers. You can do this too by this way : b^2-4ac= D X= (-b(+or-)d^1/2)/2a
So all the zeros 2, -1 and -3 If you want more explanation, send me a comment x