Question

find answer for this

Answer 1

1/v+1/u=1/f where f is 20cm for concave f is negative and u =-40cm then put in eqn v=-40 means objet is placed at c and image is also at c same in size inverted , another Q's ans is m=v/u=f+u/f where m is 1/3 f is 20 for conex lens it is positive then u=-40/3