How do you factor 2n2 9n-81?

Answer 1

6n² - 18n - 18 = 6, so 6n² - 18n - 24 = 0.

Dividing by 6:

n² - 3n - 4 = 0.

What multiplies to -4 and adds to -3? The only possible factors are:

(-1)4

(-2)2

(-4)1

...with sums of 3, 0, and -3, respectively. We want that last one, so

n² - 3n - 4 = (n - 4)(n + 1).

Answer 2

-2n(n-9) = 0

n = 0 or n = 9

Answer 3

(n + 2)(2n-9)

Answer 4

(n + 9)(2n - 9)