Final answer:
The differential equation provided is incomplete, but the question may pertain to the formula for the focal length of a lens, which when solved correctly, is f = dodi / (di + do).
Step-by-step explanation:
The student asked to find the general solution for the differential equation 46dy², but this appears to be a typo as it is not a complete differential equation.
However, another part of the question seems to refer to solving the lens formula where 1/f = 1/do + 1/di for the focal length of a lens (f), distance to the object (do), and distance to the image (di). The correct formula rearranged to solve for f is f = dodi / (di + do).