Using the preliminary factoring strategy, which method applies to r^2 - 10r - 24?

1. The polynomial r squared minus 10r minus 24 has no common factor shared by all terms, so the GCF step does not apply. 2. It is a trinomial, and its leading coefficient is 1, so the undo FOIL method from the previous section applies directly. 3. Grouping is reserved for polynomials with more than three terms, and the difference of squares pattern is for binomials, so neither fits a three-term trinomial like this one. _Source: OpenStax Elementary Algebra (CC BY 4.0), Ch 7 "Factoring", section 7.3 Factor Quadratic Trinomials with Leading Coefficient Other than 1_