Evaluate: `intx^2sqrt(a^6-x^6)dx`

Explanation

To evaluate the integral \( \int x^2 \sqrt{a^6 - x^6} \, dx \), we can follow these steps:

### Step 1: Substitution
We start by making a substitution to simplify the integral. Let \( u = x^3 \). Then, we differentiate to find \( du \):
\[ du = 3x^2 \, dx \implies dx = \frac{du}{3x^2} \]
From our substitution, we also have \( x^2 = u^{2/3} \).
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