Show mathematically that to produce an image that is the same size as the object in a concave mirror, the object needs to be at twice the focal length from the mirror.

Answer 1

1/o + 1/o=1/f
1/2f + 1/i=1/f
1/i=1/2f
i=2f

M=di/do= 2f/2f= 1

check my thinking.

Answer 2

I'm sorry, but I'm not really understanding this; could you please xplain?