Book edition 2nd

Author(s) James Stewart

Pages 830 pages

ISBN 9781133112280

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Short Answer

Find the critical numbers of the function.
26. \(f(x) = 2{x^3} + {x^2} + 2x\).

There is no critical point for the function.

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Step by Step Solution

TABLE OF CONTENTS :

TABLE OF CONTENTS

Step 1: Given data

The given function is \(f(x) = 2{x^3} + {x^2} + 2x\).

Step 2: Concept of Differentiation

Differentiation is a method of finding the derivative of a function. Differentiation is a process, where we find the instantaneous rate of change in function based on one of its variables.

Step 3: Determine the derivative of the function

Obtain the first derivative of the given function \(f(x) = 2{x^3} + {x^2} + 2x\).

\(\begin{aligned}{l}{f^\prime }(x) &= \frac{d}{{dx}}\left( {2{x^3} + {x^2} + 2x} \right)\\{f^\prime }(x) &= 2\frac{d}{{dx}}\left( {{x^3}} \right) + \frac{d}{{dx}}\left( {{x^2}} \right) + 2\frac{d}{{dx}}(x)\\{f^\prime }(x) &= 2\left( {3{x^{3 - 1}}} \right) + \left( {2{x^{2 - 1}}} \right)\end{aligned}\)

Apply power rule as in the equation: \(6{x^2} + 2x + 2\)

Take \({f^\prime }(x) = 0\) to obtain the critical point.

\(\begin{array}{c}6{x^2} + 2x + 2 = 0\\2\left( {3{x^2} + x + 1} \right) = 0\\3{x^2} + x + 1 = 0\end{array}\)

Step 4: Apply quadratic formula and simplify the expression

Apply quadratic formula, \(x = \frac{{ - b \pm \sqrt {{b^2} - 4ac} }}{{2a}}\) and obtain the roots.

\(\begin{aligned}{l}x &= \frac{{ - 1 \pm \sqrt {1 - 12} }}{6}\\x &= \frac{{ - 1 \pm \sqrt { - 11} }}{6}\end{aligned}\)

Thus, the roots are, \(x = \frac{{ - 1 + \sqrt { - 11} }}{6},x = \frac{{ - 1 - \sqrt { - 11} }}{6}\).

Here, the roots are not real as the discriminant \(( - 11)\) is less than 0.

Therefore, it fails to satisfy the conditions of definition of the critical numbers. Hence there is no critical point for the given function. Thus, there is no critical point for the function.

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Essential Calculus: Early Transcendentals

Answers without the blur.

Short Answer

Find the critical numbers of the function.
26. \(f(x) = 2{x^3} + {x^2} + 2x\).

Step by Step Solution

Step 1: Given data

Step 2: Concept of Differentiation

Step 3: Determine the derivative of the function

Step 4: Apply quadratic formula and simplify the expression

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Essential Calculus: Early Transcendentals

Answers without the blur.

Short Answer

Find the critical numbers of the function.26. \(f(x) = 2{x^3} + {x^2} + 2x\).

Step by Step Solution

Step 1: Given data

Step 2: Concept of Differentiation

Step 3: Determine the derivative of the function

Step 4: Apply quadratic formula and simplify the expression

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Find the critical numbers of the function.
26. \(f(x) = 2{x^3} + {x^2} + 2x\).