Please help me with this derivatives problem

Question

The curve below is called a serpentine. Find an equation of the tangent line to this curve at the point (2, 0.4).

y =(x)/(1+x^2)

Answer 1

This one is straightforward. By the quotient rule:

dy/dx = 1/(1+x²) - 2 x² /(1 + x²)² = (1 - x²) / (1 + x²)²

It is easy to verify that the point ( 2 , .4 ) lies on the curve.

Plugging x = 2 into the expression for the derivative gives

dy/dx = -3/25