g(x) = (2x-1)(x+2)(x-3)

Express g(x) in the form Ax³ + Bx² + Cx + D

I found that this was 2x³ - 3x² - 11x + 6

Find the constant a given that x+3 is a factor of g(x) + ax and Express x-3/ g(x)in partial fraction.

I can do the partial fractions part just not finding the constant

thanks