Ta có: \(\left\{{}\begin{matrix}f\left(1\right)=a-b=-2\\f\left(-1\right)=\left(-1\right)a-b=3\end{matrix}\right.\)
Cộng vế theo vế ta được:
-2b=1\(\Leftrightarrow b=-\frac{1}{2}\) \(\Rightarrow a=-2+b=-2+\left(-\frac{1}{2}\right)=-\frac{5}{2}\)
Vậy ta được hàm số \(f\left(x\right)=-\frac{5}{2}x+\frac{1}{2}\)
Ta có:
\(f\left(2\right)=-\frac{5}{2}.2+\frac{1}{2}=-\frac{9}{2}\)
\(f\left(-\frac{5}{3}\right)=\left(-\frac{5}{2}\right).\left(-\frac{5}{3}\right)+\frac{1}{2}=\frac{14}{3}\)