What is the factor for the trinomial?

Question

x^2-x-20

my question is how do you solve this because I’m trying to help my students solve this

Answer 1

Multiply the coefficient of x^2 times the number -20

You get -20

Then factor -20 so that the sum of the factors equal the coefficient of x which -1

so -5 x 4

-5 + 4 = -1

so the factors are (x - 5)(x + 4)