Finding focal length from di v. M graph

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Homework Statement

Using the di v. M graph, how would you find the focal length? The slope is 11.24. The y intercept is 8.753.

Relevant Equations

1/di + 1/do = 1/f
M = di/do
di = f (1+ di/do)

I tried di= f +fM, but that would mean slope and y int is the same when it’s not.

 

[osilmag]

If you rearrange your equation to f = di/(1+M) that might be easier to solve since your graph is di vs. M.