Solve quadratic equations with the quadratic formula
Solve a quadratic equation using the quadratic formula, and use the discriminant to determine the number of real roots. Unlimited questions, five difficulty levels, and a full worked solution every time — free.
Try one
Solve the quadratic equation using the quadratic formula.
x2 - 6x + 8 = 0
Answer: x = 2, 4
See one solved, step by step
Solve the quadratic equation using the quadratic formula.
x2 - 7x + 2 = 0
📘 Worked solution
1x2 - 7x + 2 = 0Identify a = 1, b = -7, c = 2 from the standard form ax^2+bx+c=0.
2x = (−b ± √(b2 - 4ac)) / (2a)This is the quadratic formula — it solves any quadratic equation.
3x = (7 ± √(41)) / (2)Substitute a = 1, b = -7, c = 2: b^2 - 4ac = (-7)^2 - 4(1)(2) = 41.
4√(41) = 6.4031, so x = (7 ± 6.4031)/(2)41 isn't a perfect square, so use a decimal approximation for the square root.
5x = 0.3, 6.7Compute the two values (using + and using -), then round to two decimal places.
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