Question

When the expression x squared - 3x-18 is factored completely, which is one of its factors?

Answer 1

`x^(2) - 3x - 18 = 0` factors →
`(x - 6) * (x+ 3)`

If you want to find your roots, use Bhaskara's formula

`x^(2) - 3x - 18 = 0`
a = 1; b = - 3, c = - 18

`\Delta = b^2 - 4*a*c`

`\Delta = (-3)^2 - 4*1*(-18)`

`\Delta = 9 + 72`

`\Delta = 81`


`x = (-b\pm √(\Delta) )/(2*a)`

`x = (-(-3)\pm √(81) )/(2*(-3))`

`x = (3\pm 9 )/(-6)`

`x' = (3-9)/(-6) = (-6)/(-6) \rightarrow \boxed{x' = 1}`

`x'' = (3+9)/(-6) = (12)/(-6) \rightarrow \boxed{x'' = -2}`

But, the answer to your question are the factors of the equation, here is:

ANSWER:

`(x - 6) * (x+ 3)`

x - 6 and x + 3