i need help to figure out how to simplify this expression down

Answer:
This is a tricky question.
You can pull the fraction apart but with caution.
-21/3 + (±[tex]b^{2}[/tex] - 4ac)/3
Ignore the A in the equation below, it's a bug.
[tex]\frac{-21}{3} + \frac{±b^2 - 4ac}{3}[/tex]