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Ch. 3 - Polynomial and Rational Functions
Blitzer - College Algebra 8th Edition
Blitzer8th EditionCollege AlgebraISBN: 9780136970514Not the one you use?Change textbook
Chapter 4, Problem 84

Exercises 82–84 will help you prepare for the material covered in the next section. Let f(x)=an(x4−3x2−4). If f(3)=−150, determine the value of a_n.

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Start with the given function: f(x) = an(x4 - 3x2 - 4).
Substitute x = 3 into the function to use the given value f(3) = -150. This gives: -150 = an (34 - 3 32 - 4).
Calculate the powers of 3 inside the parentheses: 34 = 81 and 32 = 9.
Simplify the expression inside the parentheses: 81 - 3 imes 9 - 4. Perform the multiplication and subtraction step-by-step.
After simplifying the parentheses, solve for an by dividing both sides of the equation by the simplified value inside the parentheses.

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Key Concepts

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

Function Evaluation

Function evaluation involves substituting a specific input value into the function's expression to find the corresponding output. In this problem, you substitute x = 3 into f(x) to find f(3), which helps in solving for the unknown coefficient a_n.
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Polynomial Functions

Polynomial functions are expressions involving variables raised to whole-number exponents combined using addition, subtraction, and multiplication. Understanding the structure of the polynomial f(x) = a_n(x^4 − 3x^2 − 4) is essential to correctly substitute values and manipulate the equation.
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Solving for an Unknown Coefficient

When a function includes an unknown coefficient, you can find its value by using given function values. Here, knowing f(3) = -150 allows you to set up an equation and solve for a_n by isolating it after substituting x = 3 into the polynomial.
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