Quadratic Formula Calculator: x = (-b + √(b² - 4ac))/2a

Quadratic Formula Calculator

𝑥 Algebra. Use the Quadratic formula formula to find root x, a, b, c: pick the value you want, type the others, and the answer updates as you go.

x = \dfrac{-b + \sqrt{b^2 - 4ac}}{2a}

This gives the + root of ax² + bx + c = 0; the other root uses −√. No real roots when b² − 4ac < 0.

Root xabc

Root x3

Pick the ○ next to the value you want to find, fill in the others, and it solves as you type.

What each letter means

Find the root x when a = 1, b = -5, c = 6.

Using x = (-b + √(b² - 4ac))/2a: Root x = 3.

x = (-b + √(b² - 4ac))/2a. This gives the + root of ax² + bx + c = 0; the other root uses −√. No real roots when b² − 4ac < 0.

Root x, a, b, c.

Put the values into x = (-b + √(b² - 4ac))/2a. For example, with a = 1, b = -5, c = 6, root x = 3.

Yes. In the calculator above, pick the circle next to any value (root x, a, b, c) and fill in the others: it rearranges the formula for you.