Question bank/JEE Main/Mathematics

JEE MainMathematicsModerateBinomial Theorem

If numerically greatest term in the expansion of (1- x)^21 has
the numerically greatest co-efficient is (x > 0) then complete set of
values of x are.

Show answer and solution
Numerically greatest coefficient is
 21C10 or  21C11\ ^{21}C_{10}\ or\ \ ^{21}C_{11}
∣ 21C10x10∣>∣ 21C9x9∣⇒x>56\left| \ ^{21}C_{10}x^{10} \right| > \left| \ ^{21}C_{9}x^{9} \right| \Rightarrow x > \frac{5}{6}
Similarly,
x<65⇒x∈(56,65)x < \frac{6}{5} \Rightarrow x \in \left( \frac{5}{6},\frac{6}{5} \right)

Source: Grass-G / M-18 Mathematics Paper 27 Nov Third.docx

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