Day 23 – Quadratic Formula

Earlier in the class, we learned how to solve quadratic equations by factoring.  This works fine, as long as we are able to successfully complete the factoring step.  For quadratics that cannot be factored, we will need to turn to alternative methods.

There are two methods we will use, the square root property (which is relatively simple, but doesn’t work in all cases), and the quadratic formula (which works for all quadratic equations).

This video gives a basic example of the square root property:

The next video includes several examples, both simple and more complicated, using the square root property:

The quadratic formula is a single formula that allows us to solve any quadratic equation, regardless of whether we can factor it or apply the square root property.  It is important when using the quadratic formula to first put the equation in standard form (make it equal to zero), so that you can correctly identify the numbers a, b, and c before plugging in.

Here are two examples of using the quadratic formula to solve a quadratic equation:



8 Responses to Day 23 – Quadratic Formula

  1. Mishii says:

    Pro Reitz,

    although i was confused with the first equation, later on i got a hang of it. the formula is a long one so I’m a bit scared of forgetting it, or misplacing signs.

  2. kgardiner17 says:

    Professor Reitz,
    As you explained to me why I must get rid of the ^2 for the square root property, I was still a bit confused. The example used was (x-1)^2=12

  3. justfg05 says:

    Justen Garner
    Professor Halleck

    I think that the quadratic equation is the best way to solve any quadratic equation. It might be longer than the other two methods but it gives you the right answer 95% of the time.

  4. edaocello says:

    Eda Ocello
    Professor Halleck

    It took me a while to remember the formula but once i keept doing problems and re-writing it over and over again i started to memorize it and get the hang of it. As long as I remember how to do the formula I have no other problems with quadratic equations. Its pretty easy actaully.

  5. candice W says:

    Candice Wright
    Prof. Halleck

    Todays class was pretty easy, I understood everything.

  6. Professor Reitz
    I’m Glad we spent a lot of time today in class going over the test rewiew sheet because there were many things i wasn’t sure of but today i grasped the concept, the videos were also very helpful. once you memorize the formula you cannot go wrong it will work with every quadratic equation which i think is great. i just hate that we have to go back to geometry

  7. Hibba says:

    Today’s lesson was easy.

  8. awiltshire says:

    Pro. Halleck
    so I wasn’t in class to learn this but I kind of got it, kinda

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