Lets simplify the function into it's correct quadratic form first, just by multiplying the parenthesis.
Y = x^2 -2x -8
Now we know that the range is from the minimum y-value to the maximum (if there is one)
In functions like this, they have the form y = ax^2 + bx + c, where c is the minimum or maximum for the given function
In this case, it's a minimum because there aren't any y points on the graph smaller than -8
That means the range is: y >= -8
