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:
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
The quadratic formula | Algebra (video) | Khan Academy The quadratic formula helps us solve any quadratic equation First, we bring the equation to the form ax²+bx+c=0, where a, b, and c are coefficients Then, we plug these coefficients in the formula: (-b±√ (b²-4ac)) (2a) See examples of using the formula to solve a variety of equations Created by Sal Khan