Chapter 5: Problem 54
Find \(f(-1)\) for each polynomial function. $$ f(x)=-5 x^{3}+4 x^{2}-7 x+9 $$
Short Answer
Expert verified
f(-1) = 25
Step by step solution
01
Identify the function and the variable
The given polynomial function is \[ f(x) = -5x^3 + 4x^2 - 7x + 9 \]. The variable to be evaluated is \( x = -1 \).
02
Substitute the variable value
Replace \( x \) with \( -1 \) in the polynomial function. This gives you \[ f(-1) = -5(-1)^3 + 4(-1)^2 - 7(-1) + 9 \].
03
Calculate each term individually
Now calculate each term: \[ -5(-1)^3 = -5(-1) = 5 \], \[ 4(-1)^2 = 4(1) = 4 \], \[ -7(-1) = 7 \], \[ 9 = 9 \].
04
Add up the calculated values
Finally, combine all the values: \[ 5 + 4 + 7 + 9 = 25 \].
05
Conclusion
Therefore, the value of the function at \( x = -1 \) is \( f(-1) = 25 \).
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Polynomial Evaluation
Polynomial evaluation is a method used to find the value of a polynomial function at a specific point. In this case, we need to find the value of the function at x = -1. To evaluate a polynomial, you substitute the given value of x into the polynomial equation and then simplify it.
For the polynomial function f(x) = -5x^3 + 4x^2 - 7x + 9, we substitute x = -1 into the equation. This means every x in the equation is replaced with -1. Next, calculate the individual terms step by step and finally sum them up to get the result.
Evaluation is a fundamental step in understanding how different values affect the polynomial, and it is crucial for solving many mathematical problems involving polynomials.
For the polynomial function f(x) = -5x^3 + 4x^2 - 7x + 9, we substitute x = -1 into the equation. This means every x in the equation is replaced with -1. Next, calculate the individual terms step by step and finally sum them up to get the result.
Evaluation is a fundamental step in understanding how different values affect the polynomial, and it is crucial for solving many mathematical problems involving polynomials.
Substitution Method
The substitution method is a straightforward technique used to evaluate functions, including polynomial functions. The key idea is to replace the variable in the function with a given value.
For example, to find f(-1) for the polynomial f(x)=-5x^3 + 4x^2 - 7x + 9, we follow these steps:
For example, to find f(-1) for the polynomial f(x)=-5x^3 + 4x^2 - 7x + 9, we follow these steps:
- Identify the function and the variable to be evaluated (in this case, x = -1).
- Replace every instance of x in the function with -1.
- Calculate each term separately and accurately.
- Sum up all the calculated values to get the final result.
Function Notation
Function notation is a way of representing functions in mathematics. It uses symbols to specify the operation applied to the input, making it easier to understand and manipulate functions. For instance, f(x) represents a function named 'f' with 'x' being the input variable.
Here, the polynomial function is written as f(x)=-5x^3 + 4x^2 - 7x + 9. When we write f(-1), it means we are asking for the value of the function f at x = -1. This notation helps us clearly indicate which value we are evaluating the function at.
Function notation is not only useful for evaluating functions but also plays a crucial role in calculus, algebra, and other mathematical fields. It provides clarity and precision, making it easier to communicate mathematical ideas effectively.
Here, the polynomial function is written as f(x)=-5x^3 + 4x^2 - 7x + 9. When we write f(-1), it means we are asking for the value of the function f at x = -1. This notation helps us clearly indicate which value we are evaluating the function at.
Function notation is not only useful for evaluating functions but also plays a crucial role in calculus, algebra, and other mathematical fields. It provides clarity and precision, making it easier to communicate mathematical ideas effectively.