[tex]2n^2+2n-12=0\\\\\implies n^2 +n-6=0\\\text{Apply quadratic formula,}~ n = \dfrac{-b \pm\sqrt{b^2-4ac}}{2a}. ~\\\\\text{In this case,}~ a=1,b=1, c= -6\\\\n=\dfrac{-1\pm\sqrt{1^2-4\cdot 1 \cdot -6}}{2\cdot 1}\\\\~~~=\dfrac{-1\pm\sqrt{1+24}}{2}\\\\~~~=\dfrac{-1\pm\sqrt{25}}{2}\\\\~~~=\dfrac{-1\pm5}{2}\\\\\text{Hence} ~ n=\dfrac{-1+5}{2} = 2 ~~\text{or}~~n = \dfrac{-1-5}2 = -3[/tex]
