How do you find the points where the graph of the function F(x)=x/(x^2+4)F(x)=xx2+4 has horizontal tangents and what is the equation?

1 Answer
Mar 28, 2016

The tangent is horizontal at (2, 1/4)(2,14) and (-2, -1/4)(2,14).
The equations of these tangents parallel to x-axis are y=+-1/4y=±14.

Explanation:

y = x/(x^2+4)xx2+4
y' = (4-x^2)/(x^2+4)^2 = 0, when x = +-2.
The points at which the tangents are horizontal are (2, 1/4) and (-2,-1/4).
The equations of 0-slope horizontal tangents are y=+-1/4.

The graph passes through the origin, with y increasing between the turning points (-2, -1/4) and (2, 1/4) and decreasing to the limit 0, outside -2<=x<2, as xto+-oo..