Where does have a tangent line parallel to the x axis?

Since the x axis, a horizontal line, has a slope of 0, the desired parallel line tangent to the given curve, will also have a slope of 0. This slope is also equal to the value of the derivative of y at the point of tangency (x_T, y_T). Hence, at this point we have

, or , or

Now we can substitute this value of x into the original equation to find the corresponding y coordinate:

Hence the points of tangency are and . See the graph.