[tex]\begin{gathered} f(x)=mx+b \\ \text{ where } \\ m=\frac{f(b)-f(a)}{b-a} \\ \\ m=\frac{-5-7}{4-(-1)} \\ \\ m=\frac{-12}{5} \\ \\ f(-1)=-\frac{12}{5}(-1)+b \\ \\ 7=\frac{12}{5}+b \\ b=7-\frac{12}{5} \\ \\ b=\frac{23}{5} \\ \\ \\ f(x)=-\frac{12}{5}x+\frac{23}{5} \end{gathered}[/tex]
