Question

How do you solve `x^2 - 3x - 18 = 0`?

Answer 1

`x_1=6` and `x_2=-3`

Explanation:

you have an Equation like this: `ax^2+bx+c=0`

Then you can use the formula for solving quadratic Equations:
`x=(-b+-sqrt(b^2-4ac))/(2a)`

so we have: `x=-(-3)(+-)sqrt((-3)^2-4*1*(-18))/(2*1)`

`x=(3+-sqrt(9+72))/2=(3+-9)/2`

`x_1=(3+9)/2=6`
`x_2=(3-9)/2=-3`