Factorise `(2x+3y)^(2)+14(2x+3y)(3x-y)-32(3x-y)^(2)`.

Explanation

To factorise the expression \( (2x + 3y)^2 + 14(2x + 3y)(3x - y) - 32(3x - y)^2 \), we will follow these steps:

### Step 1: Substitute Variables
Let:
- \( a = 2x + 3y \)
- \( b = 3x - y \)

Now, we can rewrite the expression in terms of \( a \) and \( b \):
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