Completing the Square: Solving Quadratic Equations

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Completing the Square: Solving Quadratic Equations

帖子 由 lonelytree 于 周二 九月 07, 2010 8:29 pm

Some quadratics are fairly simple to solve because they are of the form "something-with-x squared equals some number", and then you take the square root of both sides. An example would be:

(x – 4)2 = 5
x – 4 = ± sqrt(5)
x = 4 ± sqrt(5)
x = 4 – sqrt(5) and x = 4 + sqrt(5)

Unfortunately, most quadratics don't come neatly squared like this. For your average everyday quadratic, you first have to use the technique of "completing the square" to rearrange the quadratic into the neat "(squared part) equals (a number)" format demonstrated above. For example:

* Find the x-intercepts of y = 4x2 – 2x – 5.

To solve, refer to this site:
http://www.purplemath.com/modules/sqrquad.htm

lonelytree

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