Two convex lens having focal length f1 and f2 placed together the image v formed at a distance from the lens is?
1
\(\frac{{{f_2}u}}{{{f_2} + u}} \)
2
\(\;\frac{{{f_1}u}}{{{f_1} + u}} \)
3
\(\;\frac{{{f_1}{f_2}u}}{{{f_1}u + {f_2}u + {f_1}{f_2}}} \)
4
\(\frac{{{f_{1u + }}{f_2}u + {f_1}{f_2}}}{{{f_1}{f_2}u}} \)