At what distance from a convex lens of focal length 30 cm an object s…

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∴ m = $\frac{v}{m}=-\frac{1}{4}$  or  $v=-\frac{u}{4}$

As  $\frac{1}{v}-\frac{1}{u}=\frac{1}{f}$

∴ $\frac{1}{(-u / 4)}-\frac{1}{u}=\frac{1}{30}$

$-\frac{4}{u}-\frac{1}{u}=\frac{1}{30}$

or u = -150 cm