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TS EAMCET · Maths · Binomial Theorem

If \((1+x)^{15}=a_0+a_1 x+\ldots+a_{15} x^{15}, \quad\) then \(\sum_{r=1}^{15} r \frac{a_r}{a_r-1}\) is equal to

  1. A 110
  2. B 115
  3. C 120
  4. D 135
Verified Solution

Answer & Solution

Correct Answer

(C) 120

Step-by-step Solution

Detailed explanation

Given that \(\begin{aligned} &(1+x)^{15}=a_0+a_1 x+a_2 x^2+\ldots+a_{15} x^{15} \\ & \Rightarrow \quad{ }^{15} C_0+{ }^{15} C_1 x+{ }^{15} C_2 x^2+\ldots+{ }^{15} C_{15} x^{15} \\ &=a_0+a_1 x+a_2 x^2+\ldots+a_{15} x^{15} \end{aligned}\) Equating the coefficient of various powers…