Application Of Derivatives

If \(\left|f\left(x_{1}\right)-f\left(x_{2}\right)\right| \leq\left(x_{1}-x_{2}\right)^{2}\), for all \(x_{1}, x_{2} \in\) \(\mathbb{R}\). Find the equation of tangent to the curve \(y=f(x)\) at the point \((1,2)\).