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MHT CET · Maths · Application of Derivatives

Let \(\mathrm{f}(x)=5-|x-2|\) and \(\mathrm{g}(x)=|x+1|, x \in \mathrm{R}\) If \(\mathrm{f}(x)\) attains maximum value at \(\alpha\) and \(\mathrm{g}(x)\) attains minimum value at \(\beta\), then \(\lim _{x \rightarrow-\alpha \beta} \frac{(x-1)\left(x^2-5 x+6\right)}{x^2-6 x+8}\) is equal to

  1. A \(\frac {1}{2}\)
  2. B \(\frac {-3}{2}\)
  3. C \(\frac {-1}{2}\)
  4. D \(\frac {3}{2}\)
Verified Solution

Answer & Solution

Correct Answer

(A) \(\frac {1}{2}\)

Step-by-step Solution

Detailed explanation

\(\begin{aligned}
& |x-2| \geq 0 \\
& \Rightarrow-|x-2| \leq 0 \\
& \Rightarrow 5-|x-2| \leq 5
\end{aligned}\)
Maximum value of \(\mathrm{f}(x)\) is 5 .
\(\begin{aligned}
\therefore \quad & 5-|x-2|=5 \\
& \Rightarrow|x-2|=0 \\
& \Rightarrow x=2 \\
& \Rightarrow \alpha=2 \\
& |x+1| \geq 0
\end{aligned}\)
Minimum value of \(\mathrm{g}(x)\) is 0 .
\(\begin{aligned}
\therefore \quad & |x+1|=0 \\
& \Rightarrow x=-1 \\
& \Rightarrow \beta=-1
\end{aligned}\)
\(\begin{aligned}
\therefore \quad & \lim _{x \rightarrow-\alpha \beta} \frac{(x-1)\left(x^2-5 x+6\right)}{x^2-6 x+8} \\
= & \lim _{x \rightarrow 2} \frac{(x-1)(x-2)(x-3)}{(x-2)(x-4)} \\
= & \lim _{x \rightarrow 2} \frac{(x-1)(x-3)}{x-4} \\
= & \frac{(1)(-1)}{-2} \\
= & \frac{1}{2}
\end{aligned}\)