[tex]Q(a,\ 0)\ \text{therefore}\ S(-a,\ 0)[/tex]
As it is a kite, the x-coordinate of S would be the reflection of point Q's x-coordinate(a) and would become the negative of the value: -a
As S lies on the x-axis, its y-coordinate would be 0.
Therefore the answer is (-a,0).
Hope it helps!
