Formula For Factoring Trinomials (when a =1)It's always easaier to understand a new concept by looking at a specificexample so you might want to do that first. This formula works when 'a' is 1. In other words, we will use this approach whenever the coefficient in from of x2is 1.1) identify a,b, and c in the trinomial ax2 + bx+c2) write down all factor pairs of c3) identify which factor pair from the previous step sums up to b4) Substitute factor pairs into two binomialsExample of Factoring a TrinomialFactor x2 + 5x + 41) identify a,b, and c in the trinomial
ax2 + bx+ca= 1
b= 5
c= 42) write down all factor pairs of 4
(Note: since 5 is positive we only need to think about pairs that are either both positive or both negative. Remember a negative times a negative is a positve. As the chart on the right shows you -2*-2 is positive 4...so we do have to consider these two negative factors. This is probabily easier to understand if you watch our video lesson factoring trinonmials)3) identify which factor pair from the previous step sums up to c4) Substitute that factor pair into twobinomials(x +4)(x+1)5) If you'd like, you can check your work bymultiplying the two binomials and verify that you get the original trinomial(x +4)(x+1) = x2 + 5x + 4
