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For the following function, find the intervals on which the function is increasing or decreasing. \( f(x)=\sqrt{x^{2}+4} \)

Ask by Cross Salazar. in the United States
Feb 27,2025

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Answer

The function \( f(x)=\sqrt{x^{2}+4} \) is increasing when \( x \) is greater than or equal to 0 and decreasing when \( x \) is less than or equal to 0.

Solution

Analyze the function features with the analysis type as "intervals" for the function \( f(x)=\sqrt{x^{2}+4} \). Function by following steps: - step0: Find the increasing or decreasing interval: \(f\left(x\right)=\sqrt{x^{2}+4}\) - step1: Find the domain: \(f\left(x\right)=\sqrt{x^{2}+4},x \in \mathbb{R}\) - step2: Find the derivative: \(f^{\prime}\left(x\right)=\frac{x}{\sqrt{x^{2}+4}}\) - step3: Find the domain: \(f^{\prime}\left(x\right)=\frac{x}{\sqrt{x^{2}+4}},x \in \mathbb{R}\) - step4: Substitute \(f^{\prime}\left(x\right)=0:\) \(0=\frac{x}{\sqrt{x^{2}+4}}\) - step5: Swap the sides: \(\frac{x}{\sqrt{x^{2}+4}}=0\) - step6: Cross multiply: \(x=\sqrt{x^{2}+4}\times 0\) - step7: Simplify the equation: \(x=0\) - step8: Determine the intervals: \(\begin{align}&x\leq 0\\&x\geq 0\end{align}\) - step9: Choose the points: \(\begin{align}&x_{1}=-1\\&x_{2}=1\end{align}\) - step10: Find the values of the derivatives: \(\begin{align}&f^{\prime}\left(-1\right)\approx -0.447214\\&f^{\prime}\left(1\right)\approx 0.447214\end{align}\) - step11: Calculate: \(\begin{align}&x\leq 0\textrm{ is decreasing interval}\\&x\geq 0\textrm{ is increasing interval}\end{align}\) - step12: Evaluate: \(\begin{align}&\textrm{The increasing interval is}\textrm{ }x\geq 0\\&\textrm{The decreasing interval is}\textrm{ }x\leq 0\end{align}\) The function \( f(x)=\sqrt{x^{2}+4} \) is increasing on the interval \( x \geq 0 \) and decreasing on the interval \( x \leq 0 \).

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Beyond the Answer

To determine where the function \( f(x) = \sqrt{x^2 + 4} \) is increasing or decreasing, we first need to calculate its derivative. The derivative \( f'(x) \) is given by: \[ f'(x) = \frac{d}{dx} \left(\sqrt{x^2 + 4}\right) = \frac{x}{\sqrt{x^2 + 4}} \] Next, we analyze the sign of \( f'(x) \). The numerator \( x \) is positive when \( x > 0 \) and negative when \( x < 0 \). The denominator \( \sqrt{x^2 + 4} \) is always positive since the expression inside the square root is always greater than or equal to 4. Thus, we find that: - For \( x < 0 \), \( f'(x) < 0 \) (the function is decreasing). - For \( x > 0 \), \( f'(x) > 0 \) (the function is increasing). At \( x = 0 \), \( f'(0) = \frac{0}{\sqrt{0 + 4}} = 0 \), which indicates a change in monotonicity but does not contribute to interval classification. In summary, the function \( f(x) = \sqrt{x^2 + 4} \) is decreasing on the interval \( (-\infty, 0) \) and increasing on the interval \( (0, \infty) \).

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