A concave mirror gives a real image magnifies 4 times. When the object is moved 3 cm the magnification of the real image is 3 times. Find the focal length of mirror.

Explanation

To solve the problem step by step, we will use the mirror formula and the magnification formula for concave mirrors.

### Step 1: Understand the given information
We have two scenarios:
1. The first scenario has a magnification (m1) of -4 (since it is a real image).
2. The second scenario has a magnification (m2) of -3 after moving the object 3 cm away.

### Step 2: Use the magnification formula
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