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Find, correct to two decimal places, (a) the intervals on which the function is increasing or decreasing, and (b) the range of the function. $$y=10^{x-x^{2}}$$

Short Answer

Expert verified
(a) Function increases for \( x < 0.5 \) and decreases for \( x > 0.5 \). (b) Range is \((0, 10^{0.25}]\).

Step by step solution

01

Find the derivative of the function

To determine where the function is increasing or decreasing, we need to find its derivative. For the function \( y = 10^{x-x^2} \), let \( u = x-x^2 \), hence \( y = 10^u \). The derivative is found using the chain rule: \( \frac{dy}{dx} = 10^u \ln(10) \cdot \frac{du}{dx} \). We compute \( \frac{du}{dx} = 1-2x \), so \( \frac{dy}{dx} = 10^{x-x^2} \ln(10) (1-2x) \).
02

Determine where the derivative is positive or negative

To find where the function is increasing or decreasing, we set \( \frac{dy}{dx} > 0 \) for increasing and \( \frac{dy}{dx} < 0 \) for decreasing. Simplifying, \( \ln(10)(1-2x) > 0 \), implying \( 1-2x > 0 \). Solving for \( x \), we get \( x < 0.5 \). So, the function is increasing on the interval \((-\infty, 0.5)\) and decreasing on \((0.5, \infty)\).
03

Determine the range of the function

To find the range of the function \( y = 10^{x-x^2} \), we start by analyzing \( x-x^2 \), which is a downward-opening parabola with vertex at \( x = 0.5 \). The value of \( x-x^2 \) at the vertex is \( 0.5 - (0.5)^2 = 0.25 \). Therefore, \( 10^{x-x^2} \) achieves a maximum at this point, so the highest value \( y \) can reach is \( 10^{0.25} \), and for \( x \to \pm\infty \), \( y \to 0 \). Consequently, the range is \((0, 10^{0.25}]\).

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Derivative
Derivatives are a fundamental concept in calculus, used to determine the rate at which a function is changing at any given point. When applied to a polynomial function like \(y = 10^{x-x^2}\), finding the derivative helps us understand how the function behaves over different intervals.
In this case, we calculate the derivative using the chain rule, a technique used when differentiating composite functions. Our initial function can be rewritten as \(y = 10^u\) by letting \(u = x - x^2\). To find the derivative \(\frac{dy}{dx}\), apply the chain rule: differentiate the outer function first, \(10^u \ln(10)\), and multiply it by the derivative of the inner function, \(1-2x\). Consequently, \(\frac{dy}{dx} = 10^{x - x^2} \ln(10) (1-2x)\).
This derivative gives us a tool to analyze whether the function is increasing or decreasing at any point based on the sign of \(\frac{dy}{dx}\). A positive derivative indicates an increasing function, while a negative derivative indicates a decreasing one.
Increasing and Decreasing Functions
To identify the intervals where a function is increasing or decreasing, we examine the sign of its derivative. For the function \(y = 10^{x-x^2}\), the derivative \(\frac{dy}{dx} = 10^{x-x^2} \ln(10) (1-2x)\) determines this behavior.
By setting \(\frac{dy}{dx} > 0\), the function is increasing. This simplification leads us to solve \(\ln(10) (1-2x) > 0\), arriving at the condition \(1-2x > 0\). Solving gives \(x < 0.5\), indicating the function is increasing in the interval \(( -\infty, 0.5 )\).
Conversely, setting \(\frac{dy}{dx} < 0\) helps find where the function is decreasing, yielding \(1-2x < 0\). Solving for \(x\) leads to \(x > 0.5\), so the function decreases on \((0.5, \infty)\). Recognizing these intervals helps understand how the function behaves across its domain.
Function Range
The range of a function includes all possible output values, or \(y\) values, that the function can produce. For the function \(y = 10^{x-x^2}\), determining the range involves analyzing the expression \(x - x^2\), which describes a parabola opening downward.
The vertex of this parabola provides the maximum value of \(x-x^2\), located at \(x = 0.5\). Calculating at the vertex gives \(0.5 - (0.5)^2 = 0.25\). Therefore, the maximum output for \(y\) is \(10^{0.25}\), achieved at \(x = 0.5\).
As \(x\) approaches \(\pm \infty\), the term \(x-x^2\) tends to \(-\infty\), driving \(10^{x-x^2}\) towards zero. Consequently, the function range is \((0, 10^{0.25}]\), indicating \(y\) values span from just above zero up to \(10^{0.25}\). Understanding the range offers insights into the potential outputs of the function depending on \(x\) values.

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