
Concept explainers
a.
To find:The interval of unit length in which zero of the given polynomial function lie definitely, using Intermediate Value Theorem and graphing utility.
a.

Answer to Problem 97E
The required intervals are [−2,−1] and [0,1] .
Explanation of Solution
Given:
The polynomial function is g(x)=3x4+4x3−3 .
Formula/ concept used:
The Intermediate Value Theorem states that f(b) Let “ a ” and “ b ”be real numbers such that a<b . If a polynomial function such that f(a)≠f(b) , then in interval [a,b] takes on every value between f(a) and f(b) . If f(a) and f(b) are of opposite sign then a zeros surely lie in interval [a,b] .
Graph:
The graph of function g(x)=3x4+4x3−3 is shown in Figure-1 here.
We have f(a=−2)=13 and f(b=−1)=−4 , thus f(−2)>0 and f(−1)<0 , hence, there exists a zero of g(x)=3x4+4x3−3 in the intervalof unit length [−2,−1] .We see that f(−1.585)=0 , i.e., x=−1.585 is zero of polynomial function g(x)=3x4+4x3−3 .
We have f(a=0)=−3 and f(b=1)=4 , thus f(0)<0 and f(1)>0 , hence, there exists a zero of g(x)=3x4+4x3−3 in the interval of unit length [0,1] . We see that f(0.779)=0 , i.e., x=0.779 is zero of polynomial function g(x)=3x4+4x3−3 .
Conclusion:
There exists a zero of g(x)=3x4+4x3−3 in each intervals [−2,−1] and [0,1] .
b.
To find: The real zeros of polynomial function given in part (a) using graphing utility.
b.

Answer to Problem 97E
The zeros of function g(x)=3x4+4x3−3 are x=−1.585 and x=0.779 .
Explanation of Solution
Given:
The polynomial function and the graph of function g(x)=3x4+4x3−3 in part (a).
Concept used:
The value of x where the graph of function intersect or touch the x -axis is the zero of function.
Calculations:
From graph Figure-1, in part (a) we see that graph of function f(x) intersect x -axis at points (−1.585,0) and (0.779,0) .
Hence, x=−1.585 and x=0.779 are zeros of function g(x)=3x4+4x3−3 .
Conclusion:
The points x=−1.585 and x=0.779 are zeros of function g(x)=3x4+4x3−3 .
c.
To verify: The answers of part (a) using table feature of graphing utility.
c.

Explanation of Solution
Given:
The zeros of function g(x)=3x4+4x3−3 lie in intervals [−2,−1] and [0,1] .
Verification:
From the graph in Figure-1, we obtain a table of some solutions of the given polynomial function g(x)=3x4+4x3−3 as:
There is change of the function f(x) in intervals [−2,−1] and [0,1] each of length 1, these results are same as of part (a).
Thus, the results of part (a) stands verified.
Chapter 2 Solutions
Precalculus with Limits: A Graphing Approach
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