You could write the original equation as y = - 5x - 14. That's what f(x) looks to mean. In inverse interchanges x and y
The inverse is x = -5y - 14 Now solve for y
x + 14 = - 5y
y = (x + 14)/-5 I have included a graph to show these two relationships.
Red Line: y = -5x - 14
Blue Line: y = (x + 14)/-5