Let $\mathrm{f}(x)=\int \frac{x^2-3 x+2}{x^4+1} \mathrm{~d} x$, then function decreases in the interval
Let $\mathrm{f}(x)=\int \frac{x^2-3 x+2}{x^4+1} \mathrm{~d} x$, then function decreases in the interval
- $(-\infty,-2)$
- $(-2,-1)$
- $(1,2)$
- $(2, \infty)$
Solution
$\begin{aligned}
& \mathrm{f}(x)=\int \frac{x^2-3 x+2}{x^4+1} \mathrm{~d} x \\
& \Rightarrow \mathrm{f}^{\prime}(x)=\frac{x^2-3 x+2}{x^4+1}
\end{aligned}$
For $\mathrm{f}(x)$ to be decreasing,
$\begin{aligned}
& \mathrm{f}^{\prime}(x) < 0 \\
& \Rightarrow \frac{x^2-3 x+2}{x^4+1} < 0 \\
& \Rightarrow \frac{(x-1)(x-2)}{x^4+1} < 0 \\
& \Rightarrow(x-1)(x-2) < 0 \\
& \Rightarrow x \in(1,2)
\end{aligned}$
Asked in: MHT CET 2023 (14 May Shift 1)
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