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- Quadratic formula explained (article) | Khan Academy
The quadratic formula helps you solve quadratic equations, and is probably one of the top five formulas in math We’re not big fans of you memorizing formulas, but this one is useful (and we think you should learn how to derive it as well as use it, but that’s for the second video!) If you have a general quadratic equation like this:
- Quadratic equations | Khan Academy
Practice Number of solutions of quadratic equations Get 3 of 4 questions to level up!
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- Solving quadratic equations by factoring (article) | Khan Academy
Solving factored quadratic equations Suppose we are asked to solve the quadratic equation (x 1) (x + 3) = 0 Why is this a quadratic equation?
- Completing the square (video) | Khan Academy
Some quadratic expressions can be factored as perfect squares For example, x²+6x+9=(x+3)² However, even if an expression isn't a perfect square, we can turn it into one by adding a constant number For example, x²+6x+5 isn't a perfect square, but if we add 4 we get (x+3)² This, in essence, is the method of *completing the square*
- Quadratic formula review (article) | Khan Academy
The quadratic formula allows us to solve any quadratic equation that's in the form ax^2 + bx + c = 0 This article reviews how to apply the formula
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