What is the magnification of the image?

Question

The focal length of a diverging lens is negative. If f = −18 cm

 for a particular diverging lens, where will the image be formed of an object located 43 cm

 to the left of the lens on the optical axis?

Answer 1

1/f = 1/d + 1/x; x = df/(d - f) = 43·(- 18)/(43 + 18) = - 774/61 cm

k = - 774/61/43 = - 18/43