precalculas問題!! 急!!

"Find all the points on the x-axis that are 3 units from the midpoint of the line segment joining (5,2) and (-5,-6)."
The mid-point is
(5-5)/2,(2-6)/2
=(0,-2)
Let the point on the x-axis is (a,0)
Then
Since it is 3 units from the midpoint , distance is 3
√[(a-0)^2+(0+2)^2]=3
√[a^2+4]=3
a^2+4=9
a^2=5
a=√5 or -√5
So the points are (√5,0) (-√5,0)