What does it mean if the deviation in negative

No, standard deviation cannot be negative!

Step-by-step explanation:

Whenever we square something, we get a non-negative number. Since both the denominator and numerator are positive, the entire expression must be positive too.l

check above link.

graphically?   well, you graph them both, the solutions is where they both intersect each other, since there are two solutions, meaning they will meet twice, or namely the linear will run into the quadratic curve twice, and where they meet, those x,y coordinates are the solutions to the system.