Convert into factorials
3.6.9.12.15.18.21

Explanation

To convert the expression \(3 \times 6 \times 9 \times 12 \times 15 \times 18 \times 21\) into factorials, we can follow these steps:

### Step 1: Factor each term
We start by expressing each number in the product as a multiple of 3:
- \(3 = 3 \times 1\)
- \(6 = 3 \times 2\)
- \(9 = 3 \times 3\)
- \(12 = 3 \times 4\)
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