Consider the polynomial P(x)=3x3+18x2+15x. Answer the following:
a. (i) Factor out the highest common monomial factor from P(x).
b. (ii) Hence, completely factorise the resulting quadratic expression.
c. (iii) Using the factorised form obtained in part (ii), solve the equation P(x)=0 for real values of x. State all the roots clearly.