Find All X-Coordinates of Points (X, Y) on the Graph $\frac { x ^ { 3 } } { ( x + 2 ) ^ { 5 } }$

Short Answer

Find all x-coordinates of points (x, y) on the graph of Q(x) = $\frac { x ^ { 3 } } { ( x + 2 ) ^ { 5 } }$ where the tangent line is horizontal. Enter your answer as just a, or a, b where these are integers and $\text { a }$ < b.