The work done in extending a spring by `x_0` is `W_0`. Find the work done in further extension `x_0`.

Explanation

To solve the problem of finding the work done in further extending a spring by `x_0`, given that the work done in extending it by `x_0` is `W_0`, we can follow these steps:

### Step 1: Understand the Work Done on a Spring
The work done on a spring when it is extended from its natural length is given by the formula:
\[ W = \frac{1}{2} k x^2 \]
where \( k \) is the spring constant and \( x \) is the extension from the natural length.

### Step 2: Calculate Work Done for the First Extension
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