Factor the trinomial

u2 + u - 30

Since we see u² as the first term, we know that the factored form will be something like: (u ± something) (u ± something)

We also know that the sum of these 'somethings' is 1, and he product is negative 30 (because that's 1 u, and - 30). The two numbers that have a sum of 1 and a product of - 30 are 6 and - 5, so the factored form of this trinomial is (u + 6) (u - 5)

(u+6) (u-5) is the factored form because the two numbers in the factored must add up to the middle term and must have a product that's equal to the third term.