Binomial Theorem
Multinomial Expansion
JEE Main 2019
Grade 11

Question:

The number of distinct terms in the expansion of $(x + y + z)^{10}$ is:
(1) $55$
(2) $66$
(3) $78$
(4) $45$

Step-by-Step Solution

Key Concept: Each term corresponds to a choice of non-negative integers $a, b, c$ with $a + b + c = 10$ — count the number of such solutions using the standard stars-and-bars formula $\binom{n+k-1}{k-1}$.
The detailed step-by-step mathematical proof is available inside the Mathbee app workspace.
Correct Answer: (2)

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