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Q. 55

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Precalculus Enhanced with Graphing Utilities
Found in: Page 209
Precalculus Enhanced with Graphing Utilities

Precalculus Enhanced with Graphing Utilities

Book edition 6th
Author(s) Sullivan
Pages 1200 pages
ISBN 9780321795465

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Short Answer

In Problems 39–56, find the real zeros of f. Use the real zeros to factor f.

f(x)=4x5-8x4-x+2

The real zeros of f are 2, -12, and 12.

The factored form of f is (2x2+1)(2x-1)(2x+1)(x-2).

See the step by step solution

Step by Step Solution

Step 1. Finding the possible number of zeros 

The given function is f(x)=4x5-8x4-x+2

The given function is of degree five, so it has at most five real zeros.

Step 2. Use the rational zero theorem 

As all the coefficients are integers so we use the rational zeros theorem.

The factors of the constant term 2 are

p: ±1, ±2

The factors of the leading coefficient 4 are

q: ±1, ±2, ±4

So, the possible rational zeros are

pq: ±1, ±2, ±12, ±14

Step 3. Graph the polynomial function 

The graph is

From the graph, we conclude that it has three roots.

Step 4. Finding the factor 

Since 2 appears to be zero and a potential rational zero also.

By evaluating we get, f(2)=0

Thus, (x-2) is a factor of f.

Use synthetic division to factor f

So, factor f is localid="1646140146826" (x-2)(4x4-1)

Step 5. Factor the depressed polynomial 

Put depressed equation to zero and factor by grouping

4x4-1=04x4=1x4=14x=±12

Therefore, the other zeros are -12and12.

The factored form of f is (2x2+1)(2x-1)(2x+1)(x-2).

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