factor the leading term (4) and get the closest 2 multiplues 2 and 2 (2x+ )(2x+ ) we know that they are both plus since the midddle terms and end term is positive
now factor the last term(5) and get the 2 multiplues 1 and 5 (2x+1)(2x+5)=4x^2+2x+10x+5=4x^2+12x+5