At what distance from a concave mirror with a 45 cm focal le

At what distance from a concave mirror with a 45 cm focal length should an object be placed so that its image is the same distance from the mirror as the object?

Solution

object distance s

image distance S\' = s

focal length f=45 cm

1/s + 1/s\' = 1/45 ( s = s\')

object distance s = 90 cm