![]() We can factor the resulting trinomial using 6 = 2 ( 3 ) and 5 = ( 5 ) ( 1 ). This commonly overlooked step is worth identifying early.ġ2 y 3 − 26 y 2 − 10 y = 2 y ( 6 y 2 − 13 y − 5 )Īfter factoring out 2 y, the coefficients of the resulting trinomial are smaller and have fewer factors. ![]() As we have seen, trinomials with smaller coefficients require much less effort to factor. ![]() Doing this produces a trinomial factor with smaller coefficients. It is a good practice to first factor out the GCF, if there is one. The complete check is left to the reader. Next use the factors 1 and 4 in the correct order so that the inner and outer products are − 9 a b and 8 a b respectively.ġ8 a 2 b 2 − a b − 4 = ( 2 a b − 1 ) ( 9 a b + 4 )Īnswer: ( 2 a b − 1 ) ( 9 a b + 4 ). Use 2 a b and 9 a b as factors of 18 a 2 b 2. After some thought, we can see that the sum of 8 and −9 is −1 and the combination that gives this follows:įactoring begins at this point with two sets of blank parentheses. We are searching for products of factors whose sum equals the coefficient of the middle term, −1. The trinomial is prime.įirst, consider the factors of the coefficients of the first and last terms.ġ8 = 1 ⋅ 18 4 = 1 ⋅ 4 = 2 ⋅ 9 = 2 ⋅ 2 = 3 ⋅ 6 Therefore, the original trinomial cannot be factored as a product of two binomials with integer coefficients. There are no factors of 20 whose sum is 3. For example, consider the trinomial x 2 + 3 x + 20 and the factors of 20: Keep in mind that some polynomials are prime. However, if a guess is not correct, do not get discouraged just try a different set of factors. ![]() If we choose the factors wisely, then we can reduce much of the guesswork in this process. Now the check shows that this factorization is correct. This time we choose the factors −2 and 12 because − 2 + 12 = 10. ![]() Since the last term in the original expression is negative, we need to choose factors that are opposite in sign. In this case, the middle term is correct but the last term is not. When we multiply to check, we find the error. Then we have the following incorrect factorization:Ī 2 + 10 a − 24 = ? ( a + 4 ) ( a + 6 ) I n c o r r e c t F a c t o r i z a t i o n Suppose we choose the factors 4 and 6 because 4 + 6 = 10, the coefficient of the middle term. The first term of this trinomial, a 2, factors as a ⋅ a. ![]()
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