The calculator uses the quadratic formula to find solutions to any quadratic equation.
The formula is:
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.
Quadratic Formula Calculator and Solver
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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

Further Reading:
 Quadratic formula worksheets (several free printable pdfs with answer keys on the quadratic formula)
 Parabola Grapher (Graph any quadratic with roots, axis of symmetry and other options. You can save graph to desktop as image!)
 Quadratic Equations
 Other Free Math Calculators
 All roots calculated