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TS EAMCET · Maths · Binomial Theorem

If the set of all values of \(x\) for which the expansion of \((7-5 x)^{-\frac{2}{3}}\) valid is equal to \((-a, a)\), then \(5 a+7\) is equal to

  1. A 14
  2. B 21
  3. C 0
  4. D 12
Verified Solution

Answer & Solution

Correct Answer

(A) 14

Step-by-step Solution

Detailed explanation

\((7-5 x)^{-\frac{2}{3}}=(7)^{-\frac{2}{3}}\left(1-\frac{5 x}{7}\right)^{-\frac{2}{3}}\) For validation, \(\left|\frac{-5 x}{7}\right| < 1 \Rightarrow-1 < \frac{5 x}{7} < 1\) \[ \Rightarrow-7 < 5 x < 7 \Rightarrow-\frac{7}{5} < x < \frac{7}{5} \] So,…
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