Determine the points on the hyperbola x^2/9 - y^2/4 - 1 = 0 that have x=4

For the hyperbola x^2/9 - y^2/4 - 1 = 0, when x = 4 , we
have

x^2/9 - y^2/4 - 1 =
0

=> 4^2 / 9 - y^2 / 4 - 1 =
0

=> y^2 / 4 = 4^2 / 9  -
1

=> y^2 / 4 = 16 / 9  -
9/9

=> y^2 / 4 =
7/9

=> y^2 =
7*4/9

=> y = (2/3)*sqrt 7 and y = -(2/3)sqrt
7

So the points on the hyperbola that have x = 4
are

(4 , (2/3)*sqrt 7) and ( 4 , -(2/3)sqrt
7)