If x and y are real number such that `x^2 +2xy-y^2=6`, find the minimum value of `(x^2+y^2)^2`

Explanation

To find the minimum value of \( (x^2 + y^2)^2 \) given the constraint \( x^2 + 2xy - y^2 = 6 \), we can follow these steps:

### Step 1: Parameterization
We will use the parameterization:
\[ x = r \cos \theta, \quad y = r \sin \theta \]
This allows us to express \( x^2 + y^2 \) in terms of \( r \) and \( \theta \).
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