If `(n+1)! =90[(n-1)!],` fin d n

Explanation

To solve the equation \((n+1)! = 90 \cdot (n-1)!\), we can follow these steps:

### Step 1: Rewrite the Factorials
We start by rewriting \((n+1)!\) in terms of \(n\):
\[ (n+1)! = (n+1) \cdot n \cdot (n-1)! \]
So we can substitute this into the equation:
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