Question

an object is placed at a distance of 10 cm from the pole of a concave mirror its image is formed at 6 cm from its pole then the focal length of the mirror?

Answer 1

always imagine the case of image formation
when solving the problem like this
u= -10
v = -6
1/f = 1/v + 1/u
1/f = -1/6 + (-1/10)
1/f = (-5-3)/30
1/f = -8/30
f = -30/8
f = -3.75cm