Question

The number of values of r satisfying ³9C₃r-1=³9Cᵣ²-1=³9C₃r is

• A. 1
• B. 2
• C. 3
• D. 4

Hint:

For combinations, equal values imply equal or complementary indices.

Answer 1

The Correct Option is A

Step 1: Use property ⁿCₐ=ⁿCb⟹ a=b or a+b=n.
Step 2: Solving gives r=3 as the only integer solution.