The formula is:
$
\frac{ -b \pm \sqrt{b^2 -4ac}}{2a }
$

The quadratic formula calculator below will
solve any quadratic equation
that you type in. Simply type in a number for 'a', 'b' and 'c' then hit the 'solve' button.

The calculator on this page shows how the quadratic formula operates, but if you have access to a
graphing calculator you should be able to solve quadratic equations,
even ones with imaginary solutions.

Step 1) Most graphing calculators like the TI- 83 and others allow
you to set the "Mode" to "a + bi" (Just click on 'mode' and select 'a+bi').

If you can set your calculator's mode to a + bi you should be able to even calculate imaginary solutions.

The rest of the steps just involve typing in a,b and c. Make sure that you divide the entire numerator by 2a,
just use parentheses.