What is the distance of the image from the mirror? round the answer to the nearest whole number.
–5 cm
5 cm
–21 cm
21 cm

the mirror formula shows that 1/u+1/v=1/f where u is the object distance, v the image distance and f the focal length of the mirror.

substituting for the values from the table, that is f=13cm and u= 8cm we get:

1/8+1/v=1/13

1/v=1/13-1/8

1/v= -5/104

v= -104/5

v= -20.8

therefore the correct answer is -21cm