
Jennifer Q. answered 04/13/13
Accomplished Math, Science, and Test Prep Tutor
A "trick" to factoring trinomials is to use the product-sum method which, when the trinomial is written as x^2+Bx+C, begins with finding two numbers which add to equal B and multiply to equal C.
In the problem given, x^2 + 4x + 3, the B value is 4 and the C value is 3. The two numbers which add to 4 and multiply to 3 are +3 and +1 ( 3+1=4 and 3x1=3 ), therefore, your factorization will be (x+1)(x+3).