Explanation:
step 1. a diverging lens is "concave" on both side and always has a negative focal length
step 2. so 1/f = 1/s + 1/s' where f is the focal length, s is the object location, and s' is the image location (f, s, s' are all on the left side of the lens)
step 3. 1/-15 = 1/s + 1/-9 (image is virtual (negative))
step 4. 3/-45 = 1/s + 5/-45
step 5. s = 22.5cm (object is 22.5cm from lens)
step 6. s'/s = 9/22.5 ÷ 0.4 (magnification)
step 7. if the object is 4.5cm then the image is 4.5(0.4) = 1.8cm tall.
