x^2 - x - 3 =0

giúp mình với

`x^2 - x - 3 =0`

`<=>x-2.(1)/2.x+1/4-13/4=0`

`<=> (x-1/2)^2=13/4`

`<=>`\(\left[ \begin{array}{l}x-\dfrac{1}{2}=\dfrac{\sqrt{13}}{2}\\x-\dfrac{1}{2}=-\dfrac{\sqrt{13}}{2}\end{array} \right.\)

`<=>`\(\left[ \begin{array}{l}x=\dfrac{\sqrt{13}}{2}+\dfrac{1}{2}\\x=\dfrac{-\sqrt{13}}{2}+\dfrac{1}{2}\end{array} \right.\)

`<=>`\(\left[ \begin{array}{l}x=\dfrac{1+\sqrt{13}}{2}\\x=\dfrac{1-\sqrt{13}}{2}\end{array} \right.\)

Vậy Phương Trình có nghiệm 

`S={\frac{1+\sqrt{13}}{2};\frac{1-\sqrt{13}}{2}}`