Question

an object 4cm high is placed at a distance of 6 cm in front of a concave mirror of focal length 12 cm . find the position of the image formed ?

Answer 1

Focal Length, f = -12 cm
and Position of Obj., u = -6cm

So, 1/f = 1/v + 1/u
  so, -1/12 = 1/v -1/6
      so, 1/v = 1/6 -1/12
            1/v =  2-1/12 = 1/12
       So, Position of Image, v = 12 cm

Answer 2

hey..
here's ur solution!!

given ,
f = -12
u = -6
v = ?

using the below expression,

1/f = 1/u + 1/v

1/v = 1/f - 1/u

-1 /12 - (-1)/6

-1+2/12

1/12

hence ,
v= 12

therefore, the position of the image is 12 cm behind the mirror i. e. VIRTUAL AND ERECT.

HOPE IT HELPS!!