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TS EAMCET · Maths · Binomial Theorem

If \(\mathrm{C}_0, \mathrm{C}_1, \mathrm{C}_2, \ldots, \mathrm{C}_8\) are the binomial coefficients in the expansion of \((1+x)^8\) then \(\sum_{r=1}^8 r^3 \frac{\mathrm{C}_r}{\mathrm{C}_{r-1}}=\)

  1. A \(540\)
  2. B \(336\)
  3. C \(105\)
  4. D \(270\)
Verified Solution

Answer & Solution

Correct Answer

(A) \(540\)

Step-by-step Solution

Detailed explanation

\( \frac{\mathrm{C}_r}{\mathrm{C}_{r-1}} = \frac{8-r+1}{r} = \frac{9-r}{r} \) \( \sum_{r=1}^8 r^3 \frac{9-r}{r} = \sum_{r=1}^8 r^2 (9-r) = \sum_{r=1}^8 (9r^2 - r^3) \) \( = 9 \sum_{r=1}^8 r^2 - \sum_{r=1}^8 r^3 \)…