Question

The term independent of x in the expansion of (9x - 13√(x))¹8, x>0, is a times the corresponding binomial coefficient. Then a is:

• A. 3
• B. (1)/(3)
• C. −(1)/(3)
• D. None of these

Hint:

Constant term exists only if power of x becomes zero for integer r.

Answer 1

The Correct Option is D

Step 1: General term. Tᵣ+₁ = 18r(9x)¹⁸⁻ʳ(-x⁻¹/³)ʳ
Step 2: Power of x. 18-r - (r)/(3) = 0 r = (54)/(4) Z
Step 3: Conclusion. No constant term exists.