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COMB2 · 1

Counting

10 concepts · 25 questions

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COMB2Step●○○○○new1 Counting

Step 1 of 3 towards a full problem

The problem

How many solutions does $x_1 + x_2 + x_3 = 15$ have with $0\le x_i\le6$ ? (a) Count without the upper bounds. (b) Count solutions with $x_1\ge7$ . (c) Combine by inclusion–exclusion.

Count unrestricted solutions.