Factoring trinomials with a leading coefficient other than one, such as 2x² or -8x², requires additional strategies beyond simple factoring. One effective approach is the trial and error method, which involves making educated guesses for binomial factors and testing them using the FOIL technique until the original trinomial is reconstructed.
To factor a trinomial like 2x² + 11x + 5, start by identifying pairs of factors for the first term and the last term. The first terms of the binomials must multiply to the leading term, 2x², so possible pairs include x and 2x. The last terms must multiply to the constant term, 5, so possible pairs are 1 and 5. By testing combinations such as (x + 1)(2x + 5) and (x + 5)(2x + 1) using FOIL, you find that (x + 5)(2x + 1) expands back to the original trinomial, confirming the correct factorization.
The FOIL method involves multiplying the First terms, Outside terms, Inside terms, and Last terms of the binomials and then combining like terms. This process ensures the factors multiply correctly to the original trinomial.
For more complex trinomials like 6x² + 19x - 7, begin by listing all factor pairs of the leading coefficient and the constant term, considering their signs carefully. For example, factors of 6x² include 3x and 2x, or x and 6x. Factors of -7 include 7 and -1 or -7 and 1. Then, create all possible binomial pairs from these factors.
Instead of testing every combination with FOIL, focus on the sum of the products of the outside and inside terms, which must equal the middle term, 19x. For example, testing (3x - 1)(2x + 7) involves calculating 3x × 7 = 21x and -1 × 2x = -2x, which sum to 19x, matching the middle term. This confirms the correct factorization without exhaustive FOIL expansion.
In summary, factoring trinomials with a leading coefficient other than one involves identifying factor pairs of the first and last terms, then using the FOIL method and the sum of the inner and outer products to find the correct binomial factors. This trial and error approach, combined with strategic testing, streamlines the factoring process for more complex polynomials.