Factorize :
x^2+3x+2+ ax+2a

x²+3x+2+ax+2a              
x²+2x+x+2+a(x+2)          [ As x²+3x+2 is a quadratic equation 'a' is common in 'ax+2a' ]
x(x+2)+1(x+2)+a(x+2)    [(x+2) is common in all ]
(x+1+a) (x+2)