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How to derive the quadratic formula.

How to solve a general quadratic equation for x to find the quadratic formula.

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The quadratic formula (x = (-b ± √(b²- 4ac))/2a) is the easiest way to solve an equation of the form ax² + bx + c = 0. But why is the formula true?

We start with a general quadratic equation: y = ax² + bx + c. Here, x and y are unknown variables, and a, b, and c stand for any number (we use the letters instead of specific numbers to show that the quadratic formula will work no matter what numbers we plug in to a, b, and c).

We want to know what values for x will make y equal to zero. ...

Solution Summary

This solution has a proof of the quadratic formula.