How do you factor 2n^2+3n-9

Find the factors that multiply to give 2n^2 and - 9 but add to give 3n.

2n and n give 2n^2

-3 and 3 give - 9

2n*3=6n ... (1)

n * (-3) = - 3n ... (2)

(1) + (2) = 3n

Group the factors that do not have an effect/interaction to each other from the above.

That is, 2n and - 3, and n and 3

2n^2+3n-9 = (2n-3) (n+3)