Question 0111b

Given that the curve with equation ${y=f(x)}$ passes through the points with coordinates ${(-2.1, 1.1),}$ ${(2.1, 9.0)}$ and ${(2.8, 11.3),}$ find the values of ${a,b}$ and ${c.}$ Give your answers correct to 3 decimal places.

Find the set of values of ${x}$ for which ${f(x)}$ is a decreasing function.