Solving Quadratic Equations using the Quadratic Formula

Algebra II: Solving Quadratic Equations using the Quadratic Formula

This is a free lesson from our course in Algebra II


	This lesson explain another approach for solving quadratic equation i.e. using the quadratic formula. You'll find here some examples with solution, and the instructor explains all that with the help of audio, video presentation and in own hand writing. The quadratic formula gives an alternative to Completing the Square when you cannot factor an equation. It will always yield an answer, whether the quadratic was factorable or not. In the Quadratic Formula: ax² + bx + c = 0, the value of x is given by x = {-b(b² - 4ac)}/2a. (More text below video...)

Other useful lessons:

Finding a Quadratic Equation given the roots

(Continued from above) To find the solutions to an equation, we simply need to identify what a, b, and c are, then substitute them into this formula, and simplify. For example, solve x² - 6x + 4 = 0. Here a=1, b=-6 and c=4. Substituting them into the formula:
x = {-(-6)

((-6)² - 4(1)(4))}/2(1)
x = {6

(36 - 16)}/2
x = {6

(20)}/2
x = {6

5}/2
x = 3

5.
Note: When using the Quadratic Formula, you make sure not to omit the '

'sign, and be careful with the fraction line (it's under the initial b part, too).

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