Rational Completeing the Square

  • Thread starter ISX
  • Start date
  • #1
ISX
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Homework Statement


51v52u.jpg



Homework Equations


9fxswl.jpg


The Attempt at a Solution


Alright so the solution is in the above pic, but I can't get anywhere close. You can see from the green circles that the "squares" aren't matching up. So I'm not sure if I can't multiply fractions anymore or what.
2ivzmoj.jpg
 

Answers and Replies

  • #2
SammyS
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Homework Statement


[ IMG]http://i49.tinypic.com/51v52u.jpg[/PLAIN]

Homework Equations


[ IMG]http://i50.tinypic.com/9fxswl.jpg[/PLAIN]

The Attempt at a Solution


Alright so the solution is in the above pic, but I can't get anywhere close. You can see from the green circles that the "squares" aren't matching up. So I'm not sure if I can't multiply fractions anymore or what.
[ IMG]http://i47.tinypic.com/2ivzmoj.jpg[/PLAIN]
Your line

[itex]\displaystyle x^2-\frac{5}{6}x+\frac{25}{144}=-\frac{1}{6}+\frac{25}{144}[/itex]

is correct.

What your last line shows (correctly) is that [itex]\displaystyle \left(x-\frac{5}{6}\right)^2\ne x^2-\frac{5}{6}x+\frac{25}{144}\ .[/itex]

When you square 5/6, you don't get 25/144 .

How did you get 25/144 in the first place? You squared 5/12 not 5/6 .
 

Attachments

  • #3
81
1
you went from
[itex]x^2 +bx + (\frac{b}{2})^{2}[/itex]
to
[itex](x+b)^{2}[/itex]

and not to

[itex](x+\frac{b}{2})^{2}[/itex]
 
  • #4
ISX
120
0
Hellllllll I've been doing it wrong for centuries then. Lets try this again.

2exspdu.jpg


2128lz5.jpg


Ahhhh! Thanks for the help guys! I was always just dropping the last number off and went with the first 2. Guess I never caught on that fractions didnt work that way.
 

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