One way to factor equation is to find the zeros. Its obvious that x=-1 is solution for this. So one factor is (x+1)
the next factor should include 2x at first (because we have 2x^2 in the equation which can not be made any other way)
Let's suppose the factor is (x+1)(2x+b)
Since we do not know what is b open the brackets 2x^2+bx+2x+b. If this is equal to 2x^2+5x+3 then b=3. We are left with (x+1)(2x+3)=2(x+1)(x+3/2)
Would go for other shorter solutions, but they require some deeper understanding like Horner's scheme,Fermat's Theorem or even deeper which I assume You will not understand)
