Completing the Square

The GNARLY world of deriving the quadratic formula!

Hi everyone! This site is brought to you by Sara Butler and Amanda Davidson.

We’re just a couple of everyday PreCal students that like to make web pages. Yeah right!! We’re really blessing you with this page to share some of our knowledge and give you an idea of what you’ve gotten yourself into if you’re taking PreCal next year!

Here we go!!!!

Equation of a quadratic: y =

Set to Zero: = 0

Subtract the constant: =

Divide the coefficient of :

Add one half of the linear coefficient to both sides:

Factor:

Take the square root of both sides:

Isolate x:

Solve for x:

Variation: If you feel like being adventurous, here’s something for ya! Hint: See if you can figure out what is a,b,c and x.

Equation:

Now that you have the hang of completing the square (hopefully), you can use this to help you solve quadratic equations that you aren’t able to factor. Ex:

LINKS:

Here are some BODACIOUS links to other related sites!

http://www.hawaii.edu/suremath/jcompletingSquare.html

http://www.purplemath.com/modules/sqrquad.htm

http://www.ltcconline.net/greenl/courses/152B/QuadraticsLineIneq/quadfor.htm

http://www.fayar.net/east/teacher.web/math/young/index.html

http://library.thinkquest.org/29292/quadratic/3solving/2complete/

http://www.gomath.com/htdocs/lesson/quadratic_lesson3.htm

http://www.alltel.net/~okrebs/page6.html