3x^2 + 11x + 10
first ask what multiplies to make 3x^2 (3x )(x )
then what multiplies to make 10 (2 and 5) the question is where to put each number (this is where trial and error comes in
if you start with (3x + 2)(x + 5) and FOIL you get 3x^2 + 15x + 2x + 10....notice that 15x + 2x = 17x not the 11x that you need
so try again, but switch the 2 and 5 (3x + 5)(x + 2) then 3x^2 + 6x + 5x + 10...notice that 6x + 5x = 11x
so answer is (3x + 5)(x + 2)