If \(\lim _{x \rightarrow \infty}\left(1+\frac{p}{x}\right)^{q x}=e^9\) where \(p, q \in \mathbf{N}\) then…
If \(\lim _{x \rightarrow \infty}\left(1+\frac{p}{x}\right)^{q x}=e^9\) where \(p, q \in \mathbf{N}\) then \(p+q=\)
- 6
- 9
- 81
- 18
Solution
Given, \(\lim _{x \rightarrow \infty}\left(1+\frac{p}{x}\right)^{q x}=e^9\),
Let \(\frac{1}{x}=y \Rightarrow\) When \(x \rightarrow \infty \Rightarrow y \rightarrow 0\)
\(\therefore \lim _{y \rightarrow 0}(1+p y)^{q / y}=e^9\)
\(\Rightarrow \quad\left\{\lim _{y \rightarrow 0}(1+p y)^{1 / y}\right\}^q=e^9\)
\(\Rightarrow \quad\left(e^p\right)^q=e^9 \Rightarrow p q=9\)
Let we take \(p=3 \Rightarrow q=3\) and \(\therefore p+q=6\)
Asked in: AP EAMCET 2020 (17 Sep Shift 2)
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