Solving with the quadratic formula - Watch video (Algebra I)

Algebra I: Solving with the quadratic formula

This is a free lesson from our course in Algebra I


	In this section, you'll learn another approach to using the quadratic formula. If the left hand side of a given equation ax² + bx + c = 0 cannot be factorized easily into the product of a pair of binomials, then it can be solved by using the quadratic formula x = {-b (b² - 4ac)}/2a and it'll have two roots. For example, if you use the quadratic formula to solve equation x² + 2x + 7, you get two roots x = -1 22. There are some quadratics (most of them, actually) that you can't solve by factoring. But the Quadratic Formula will always work, whether the quadratic was factorable or not.(More text below video...)

People who saw this lesson also found the following lessons useful:

Solve 2nd order polynomial by factoring

Solution and discriminant in the quadratic formula

Factoring by grouping

	(Continued from above) For example, use the Quadratic Formula to solve x² � 4x � 8 = 0. Looking at the coefficients, you see that a = 1, b = �4, and c = �8. Plug them into the Formula, and simplify. x = -(-4) � (-4)2 � 4(1)(-8) / 2(1) = 4 � (16 + 32) / 2 = 4 � 48 / 2 = 4 � 43 / 2 = 2 � 23 = 2(1 � 3) Then the solution is x = 2(1 � 3).

	As many of you know, Winpossible's online courses use a unique teaching method where an instructor explains the concepts in any given area to you in his/her own voice and handwriting, just like you see your teacher explain things to you on a blackboard in your classroom. This particular lesson includes the teacher's instruction, practice questions as well as end-of-lesson quizzes for practice. As we mentioned above, you can enroll in our online course in Algebra I by clicking here. The format of Winpossible's online courses is also very suitable for teachers who are using an interactive whiteboard such as Smartboard on Promethean in their classrooms, because the course lessons can be easily displayed on such interactive whiteboards. Volume pricing is available for schools interested in our online courses. For more information, please contact us at educators@winpossible.com.