Answer
[tex] {f}^{ - 1} (x) = \frac{5}{2} x - 5.[/tex]
Step by step
[tex]y = \frac{2x}{5} + 2[/tex]
Swap roles of x and y
[tex]x = \frac{2}{5} y + 2[/tex]
Then
[tex]5x = 2y + 10[/tex]
So
[tex]2y = 5x - 10[/tex]
Hence
[tex]y = \frac{5}{2} x - 5[/tex]
Therefore
[tex] {f}^{ - 1} (x) = \frac{5}{2} x - 5.[/tex]
