The Quadratic Formula
The Quadratic Formula
In this video, we’ll be going over the Quadratic Formula. This will be super short as it is essentially an extension of the Factorising Quadratics video but with more of a focus on the ‘solving’ side of things.
The below formula is something you need to learn for your exam.
As mentioned in the Factorising Quadratics video, quadratic formulas are usually provided in the following format —> \(ax^2 + bx + c\).
Based on this, the Quadratic Formula is as follows:
\(x=\frac{-b\pm\sqrt{b^2-4ac}}{2a}\)
There are 2 key things you need to remember when using this formula:
- Beware of the ‘$\pm$’, this indicates that it should be \(-b +…\) and \(-b-…\) so you will get 2 values for \(x\) as a result of this formula.
- If you get a negative value within your \(\sqrt{b^2-4ac}\), you have likely done something wrong and need to revisit your workings.
Now you’re probably wondering, why do I need to learn how to Factorise Quadratics to solve for \(x\) when I can just use this formula?
Well, you need to keep a close eye on what the question asks for:
- If the question mentions to leave you answer to a certain number of decimal points or significant figures.
- If the questions wants you to leave your answer as a surd.
Hopefully, this all made sense. Now give some practice questions a go from the section below!
If you’ve got any questions, please feel free to leave them in the comments and I’ll get back to you as soon as possible.