Answer :
[tex]y^2 -6y-66=0\\y1 = \frac{-b+\sqrt{b^2-4ac}}{2a}\\y2 = \frac{-b-\sqrt{b^2-4ac}}{2a}\\= \frac{6+\sqrt{300}}{2}\\= \frac{6-\sqrt{300}}{2}\\[/tex]
[tex]y = 3+5\sqrt{3}\\ y = 3-5\sqrt{3}[/tex]
[tex]y^2 -6y-66=0\\y1 = \frac{-b+\sqrt{b^2-4ac}}{2a}\\y2 = \frac{-b-\sqrt{b^2-4ac}}{2a}\\= \frac{6+\sqrt{300}}{2}\\= \frac{6-\sqrt{300}}{2}\\[/tex]
[tex]y = 3+5\sqrt{3}\\ y = 3-5\sqrt{3}[/tex]