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Q9E

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Essential Calculus: Early Transcendentals
Found in: Page 215
Essential Calculus: Early Transcendentals

Essential Calculus: Early Transcendentals

Book edition 2nd
Author(s) James Stewart
Pages 830 pages
ISBN 9781133112280

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Short Answer

9–12 ■ Verify that the function satisfies the hypotheses of the Mean Value Theorem on the given interval. Then find all numbers \(c\) that satisfy the conclusion of the Mean Value Theorem.

9. \(f(x) = 2{x^2} - 3x + 1\), \((0,2)\)

The numbers \(c = 1\) satisfies the conclusion of Mean Value Theorem.

See the step by step solution

Step by Step Solution

Step 1: Given

The function \(f(x) = 2{x^2} - 3x + 1\) is a polynomial.

Step 2: Concept of Mean Value Theorem

Assume \(f\) to be a function satisfying the following properties.

(1) \(f\)Continuous on the interval \((a,b)\).

(2) \(f\) Is differentiable on the interval \((a,b)\).

Then there is a number \(c\) in \((a,b)\) such that \({f^\prime }(c) = \frac{{f(b) - f(a)}}{{b - a}}\).

Or, equivalently, \(f(b) - f(a) = {f^\prime }(c)(b - a)\).

Step 3: Check the conditions of Mean Value Theorem

  1. Since the function \(f(x) = 2{x^2} - 3x + 1\) is a polynomial function, it is continuous on\(R\).

Therefore, the function is continu\(f(x)\)ous on the closed interval \((0,2)\).

2. Since the function \(f(x) = 2{x^2} - 3x + 1\) is a polynomial function, it is differentiable everywhere.

Therefore, the function is differentiable on the open interval \((0,2)\).

Hence, the function \(f(x)\) satisfies the conditions of Mean Value Theorem.

Since the number c satisfies the conditions of Mean Value Theorem, it should lie on the open interval \((0,2)\).

Step 4: Differentiate the function and find the values

Find the derivative of .

\(\begin{aligned}{c}{f^\prime }(x) &= \frac{d}{{dx}}\left( {2{x^2} - 3x + 1} \right)\\ &= 2(2x) - 3(1) + 0\\ &= 4x - 3\end{aligned}\)

Replace \({\rm{x }} \to c\) in \({f^\prime }(x)\).

\({f^\prime }(c) = 4c - 3\)

Obtain the functional values at the end points of the given interval.

Substitute \(0{\rm{ }} \to x\) in \(f(x)\).

\(\begin{aligned}{c}f(a) &= f(0)\\ &= 2{(0)^2} - 3(0) + 1\\ &= 1\end{aligned}\)

Substitute \(2{\rm{ }} \to x\) in \(f(x)\).

\(\begin{aligned}{c}f(b) &= f(2)\\ &= 2{(2)^2} - 3(2) + 1\\ &= 8 - 6 + 1\\ &= 3\end{aligned}\)

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