How to Calculate Focal Length of a Convex Mirror?

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To calculate the focal length of a convex mirror when the virtual image is one-quarter the size of the object, the formula 1/di = 1/f - 1/do is used. The image distance (di) is found to be -9.3 cm, and the object distance (do) is 37 cm. When substituting these values into the equation, the calculations need to be carefully checked to avoid errors. The correct approach involves rearranging the formula to isolate f and ensuring all signs are appropriately accounted for. Accurate calculations will yield the correct focal length for the convex mirror.
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Homework Statement


The virtual image produced by a convex mirror is one-quarter the size of the object.
b) What is the focal length of this mirror?

Homework Equations



1/di = 1/f - 1/do

The Attempt at a Solution


i found di to be -9.3 cm but when i solved for f i keep getting it wrong. Help! (and -9.3 is correct so that's not the problem)
 
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Can you show your calculations?
 
i did 1/-9.3 = 1/f - 1/37 (do) then solved for f
 

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