i think what you should be doing is equating dy/dx to 0 since it says that the tangent is parallel to the x-axis which means gradient of the line should be 0.
Then you would get the x coordinate(s) which you can sub back into y to find the y coordinate(s)

by subing x=0 into dy/dx you are actually just finding the gradient of tangent to the curve at x=0 thats why it gave you the value of negative square root 1/2

So is this correct?

I tried to equate Dy/DX =0 but I got X=2 and I.

i think x=2 is the answer just sub back into y to get y-coordinates

the tangent is also parallel to the x-axis so gradient cannot be negative square root 1/2

Ok. Thank you