If (x-3) is a factor of 3x^3+bx^2-17x-12.

Question

a. Find the value of b.
b.Hence , find the roots fo the equation 3x^3+bx^2-17x-12=0.

Answer 1

if x=3, then f(x)=0, so put in x=3 into f(x)=0 and solve for b.

Now that you know b, you can divide out the factor (x-2) and are left with a quadratic 3x^2+ ... which if =0, then you can factor or use the quadratic equation to find those two roots.