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Ch. 4 - Applications of Derivatives
Hass - Thomas' Calculus 15th Edition
Hass15th EditionThomas' CalculusISBN: 9780137616077Not the one you use?Change textbook
Chapter 4, Problem 4.3.33

Identifying Extrema


In Exercises 19–40:


a. Find the open intervals on which the function is increasing and those on which it is decreasing.


b. Identify the function’s local extreme values, if any, saying where they occur.


g(x) = x√8 − x²

Verified step by step guidance
1
To find the intervals where the function is increasing or decreasing, first find the derivative of the function g(x) = x√(8 - x²). Use the product rule and chain rule to differentiate.
Set the derivative equal to zero to find the critical points. These points will help determine where the function changes from increasing to decreasing or vice versa.
Analyze the sign of the derivative on the intervals determined by the critical points. If the derivative is positive on an interval, the function is increasing there; if negative, the function is decreasing.
To identify local extrema, evaluate the function at the critical points. Use the first derivative test to determine if these points are local maxima or minima.
Summarize the intervals of increase and decrease, and list any local extrema along with their locations based on the analysis of the derivative and critical points.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Derivative and Critical Points

The derivative of a function provides information about its rate of change. To find where a function is increasing or decreasing, calculate its derivative and identify critical points where the derivative is zero or undefined. These points are potential locations for local extrema and help determine intervals of increase or decrease.
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Critical Points

Increasing and Decreasing Intervals

A function is increasing on an interval if its derivative is positive over that interval, and decreasing if the derivative is negative. By analyzing the sign of the derivative across different intervals, you can determine where the function rises or falls, which is crucial for identifying behavior patterns in the function.
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Determining Where a Function is Increasing & Decreasing

Local Extrema

Local extrema refer to the local maximum or minimum values of a function within a specific interval. These occur at critical points where the derivative changes sign. To identify local extrema, evaluate the function at critical points and use the first or second derivative test to confirm whether these points are maxima or minima.
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Finding Extrema Graphically
Related Practice
Textbook Question

Theory and Examples


Maximum height of a vertically moving body The height of a body moving vertically is given by s = −12gt² + υ₀t + s₀,  g > 0, with s in meters and t in seconds. Find the body’s maximum height.

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Textbook Question

Business and Economics

62. Production level Suppose that c(x)=x^3-20x^2 + 20,000x is the cost of manufacturing x items. Find a production level that will minimize the average cost of making x items.

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Textbook Question

56. Airplane landing path An airplane is flying at altitude H when it begins its descent to an airport runway that is at horizontal ground distance L from the airplane, as shown in the accompanying figure. Assume that the landing path of the airplane is the graph of a cubic polynomial function y = ax^3+bx^2+cx+d, where y(-L)= H and y(0)=0.

a. What is dy/dx at x = 0?

b. What is dy/dx at x = -L?

c. Use the values for dy/dx at x = 0 and x =- L together with y(0) = 0 and y(-L) = H to show that y(x)=H[2(x/L)^3+3(x/L)^2]

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Textbook Question

The 8-ft wall shown here stands 27 ft from the building. Find the length of the shortest straight beam that will reach to the side of the building from the ground outside the wall.

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Textbook Question

Finding Indefinite Integrals


In Exercises 17–56, find the most general antiderivative or indefinite integral. You may need to try a solution and then adjust your guess. Check your answers by differentiation.


∫(−3csc²x)dx

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Textbook Question

Initial Value Problems

Solve the initial value problems in Exercises 71–90.

d³y/dx³ = 6; y″(0) = −8, y′(0) = 0, y(0) = 5

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