complete the square

soprano

New member
Joined
Jan 29, 2010
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12
I don't understand how to do this problem at all.
12x^(2) + 13 x = 4
Can someone help please

I received a reply but I still do not understand where the 361/576 comes from in completing the square.
 
12x2+13x = 4      12x2+13x4 = 0.\displaystyle 12x^{2}+13x \ = \ 4 \ \implies \ 12x^{2}+13x-4 \ = \ 0.

12[x2+13x1213] = 0\displaystyle 12\bigg[x^{2}+\frac{13x}{12}-\frac{1}{3}\bigg] \ = \ 0

12[(x+1324)2361576] = 0, this completes the square.\displaystyle 12\bigg[\bigg(x+\frac{13}{24}\bigg)^{2}-\frac{361}{576}\bigg] \ = \ 0, \ this \ completes \ the \ square.

Check: 12[x2+26x24+169576361576] = 0\displaystyle Check: \ 12\bigg[x^{2}+\frac{26x}{24}+\frac{169}{576}-\frac{361}{576}\bigg] \ = \ 0

= 12[x2+13x12192576] = 0\displaystyle = \ 12\bigg[x^{2}+\frac{13x}{12}-\frac{192}{576}\bigg] \ = \ 0

=12[x2+13x1213] = 0\displaystyle =12\bigg[x^{2}+\frac{13x}{12}-\frac{1}{3}\bigg] \ = \ 0

= 12x2+13x4 = 0\displaystyle = \ 12x^{2}+13x-4 \ = \ 0

Your query: 169576+k = 13, k being the unknown we wish to know.\displaystyle Your \ query: \ \frac{169}{576}+k \ = \ -\frac{1}{3}, \ k \ being \ the \ unknown \ we \ wish \ to \ know.

Hence, k = 13169576 = 361576, capishe.\displaystyle Hence, \ k \ = \ -\frac{1}{3}-\frac{169}{576} \ = \ -\frac{361}{576}, \ capishe.
 
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