Question on completing the square  TOPIC_SOLVED

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Question on completing the square

Postby geramul on Tue Nov 20, 2012 10:45 pm

Something about the lesson given here confuses me. I understand how to complete the square, but this is bothering me and I need to know why this happens.

So we have sample question 4x2 - 2x - 5 = 0

I understand everything up until I have to convert the left side to squared form, let me show you why.

-2x becomes -1/2x, which becomes - 1/4 which becomes 1/16. Now we add 1/16 to both sides.

x2 - 1/2x + 1/16 = 5/4 + 1/16.

Now we have (x - 1/4)2 = 21/16

My question is, what happened to the 1/16 on the left side? It can't be added to 1/2x right? So for a while I was wondering how 1/2 became 1/4, but I figured it becomes 1/4 when I convert the left side to squared form. So where does that 1/16 go? Do we just assume it vanished? Something has to happen to the 1/16 on the left side, it can't just "go away" can it?
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  TOPIC_SOLVED

Postby stapel_eliz on Tue Nov 20, 2012 11:25 pm

geramul wrote:x2 - 1/2x + 1/16 = 5/4 + 1/16.

Now we have (x - 1/4)2 = 21/16

My question is, what happened to the 1/16 on the left side?

What is (x - 1/4)2 equal to, after expansion? :wink:
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Re: Question on completing the square

Postby geramul on Wed Nov 21, 2012 1:33 am

stapel_eliz wrote:
geramul wrote:x2 - 1/2x + 1/16 = 5/4 + 1/16.

Now we have (x - 1/4)2 = 21/16

My question is, what happened to the 1/16 on the left side?

What is (x - 1/4)2 equal to, after expansion? :wink:


Ahhhhhh I see. I hate and love math because of tricky dicky shit like this lol. Thanks.
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