Simplifying $\{ x \in \mathbb{R} : x^2 - x - 6 \geq 0 \}$ when possible Simplify the following interval notation when possible:
$$\{ x \in \mathbb{R} : x^2 - x - 6 \geq 0 \}$$

Read about Quadratic equation. That should give you a good idea of them, then you'll be able to find the roots. According to the roots you've found, you can figure out where the equation is positive or negative. 
Generally, $ax^2+bx+c$ has the opposite sign of $a$ between the roots. 
The given equation has $3$ and $-2$ as roots, then where it's greater than or equal to zero?
