What is the completely factored form of -6a^2 + 36a?

1. Ignoring signs, the GCF of 6a squared and 36a is 6a. 2. Since the leading coefficient of -6a squared + 36a is negative, the GCF is taken as -6a instead of positive 6a. 3. Rewrite each term using -6a: -6a squared is -6a times a, and 36a is -6a times -6. 4. Factor to get -6a(a - 6), and check by multiplying: -6a times a, plus -6a times -6, gives back -6a squared + 36a. 5. Keeping the GCF positive as 6a(a - 6) instead expands to 6a squared - 36a, which has the wrong sign on both terms. _Source: OpenStax Elementary Algebra (CC BY 4.0), Ch 7 "Factoring", section 7.1 Greatest Common Factor and Factor by Grouping_