Answer
The object is moving in the +x-direction.
Work Step by Step
The net force is in the +x-direction. Therefore, the acceleration $a_x$ is in the +x-direction. Since the change in speed is increasing, the velocity $v_x$ must be in the same direction as $a_x$. Therefore, the sign of $v_x$ is + and so the object is moving in the +x-direction.
