Solve using Quadratic Formula Question, What went wrong?

Question

Okay the question is to solve using quadratic formula and the question is $10r^2-6=0$ and after using the $-b \pm \frac{\sqrt{ b^2-4ac}}{2a}$ I got $-0 \pm \frac{\sqrt{240}}{20}$...and I don't know where to go after that...i thought about taking square root but than i get $15$ something $20$??

Answer 1

If you're required to use quadratic formula, you just need to simplify:

$\pm \frac{\sqrt{240}}{20} = \pm\frac{\sqrt{240}}{\sqrt{400}} =\pm \sqrt{\frac{240}{400}} = \pm\sqrt{\frac{3}{5}}$

Otherwise, as Feyre pointed out, there's no reason to use the quadratic formula and you can just solve it directly