An object is placed on the principal axis of a concave mirror at a...

Given,& $u = - 1 . 5f$,~ now use the mirror formula for the concave mirror, in terms of distance between object and pole, the distance between image and pole and focal length,&

$\dfrac{1}{u} + \dfrac{1}{v} = \dfrac{1}{f}⇒ \dfrac{1}{- 1 . 5f} + \dfrac{1}{v} = \dfrac{1}{- f}$

$⇒ \dfrac{1}{v} = - \dfrac{1}{f} + \dfrac{1}{1 . 5f}⇒ \dfrac{1}{v} = \dfrac{- 1 . 5 + 1}{1 . 5f} = \dfrac{- 0 . 5}{1 . 5f}$

$⇒ v = - 3f$.&