How do you find an equation from a graph? - Answers

In general, it is very difficult. Even if a graph looks like a straight line over the domain there is no guarantee that the underlying equation makes the equation non-linear as you move away from the visible domain. A typical example, from school physics, concerns Hooke's law. The extension of a length of wire under different strains follows a linear relationship. Until the strain reaches a critical level and then the relationship goes all haywire. Looking at the graph below that critical level, the equation would be a straightforward linear one. But that is true only as far as it goes.