CBSE Class 10 Answered

Yes, pritam you can equate the two formulae as they both denote one and the same thing.
Its just like equating 1= 1.

h = 5 cm
f = -10 cm
u = -15 cm

1/v + 1/u = 1/f

therefore, 1/v = 1/f - 1/u

                        = 1/(-10) - 1/(-15)

                        = (15-10)/150

                        = 5/150

                        = 1/30

thus, v = +30 cm

Now, h'/h = -v/u
Therefore, h' = h x (-v/u)
                      = (5) x (-30/-15)

                      = 10 cm.

Image is real, inverted and enlarged.