The image of a small electric bulb fixed on the wall of a room is to be obtained on the opposite wall `3 m` away by means of a large convex lens. What is the maximum possible focal length of the lens required for the purpose ?

Explanation

To find the maximum possible focal length of a convex lens required to obtain the image of a small electric bulb on the opposite wall, we can follow these steps:

### Step 1: Understand the Setup
We have two walls in a room that are 3 meters apart. A small electric bulb is fixed on one wall, and we want to obtain its image on the opposite wall using a convex lens.

### Step 2: Define the Variables
Let:
- The distance from the lens to the bulb be \( x \) (this distance will be negative as per the sign convention).
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