Chapter 2: Problem 56
Find the function values. $$ f(n)=5 n^{2}+4 n $$ a) \(f(0)\) b) \(f(-1)\) c) \(f(3)\) d) \(f(t)\) e) \(f(2 a)\) (1) \(f(3)-9\)
Short Answer
Expert verified
a) \(f(0) = 0\), b) \(f(-1) = 1\), c) \(f(3) = 57\), d) \(f(t) = 5t^2 + 4t\), e) \(f(2a) = 20a^2 + 8a\), (1) \(f(3) - 9 = 48\).
Step by step solution
01
Evaluate f(0)
Start by substituting 0 for n in the function \[ f(n) = 5n^2 + 4n \]\[ f(0) = 5(0)^2 + 4(0) = 0 \]So, \(f(0) = 0\).
02
Evaluate f(-1)
Substitute -1 for n in the function \[ f(n) = 5n^2 + 4n \]\[ f(-1) = 5(-1)^2 + 4(-1) = 5(1) - 4 = 5 - 4 = 1 \]So, \(f(-1) = 1\).
03
Evaluate f(3)
Substitute 3 for n in the function \[ f(n) = 5n^2 + 4n \]\[ f(3) = 5(3)^2 + 4(3) = 5(9) + 12 = 45 + 12 = 57 \]So, \(f(3) = 57\).
04
Evaluate f(t)
Substitute t for n in the function \[ f(n) = 5n^2 + 4n \]\[ f(t) = 5(t)^2 + 4(t) = 5t^2 + 4t \]So, \(f(t) = 5t^2 + 4t\).
05
Evaluate f(2a)
Substitute 2a for n in the function \[ f(n) = 5n^2 + 4n \]\[ f(2a) = 5(2a)^2 + 4(2a) = 5(4a^2) + 8a = 20a^2 + 8a \]So, \(f(2a) = 20a^2 + 8a\).
06
Evaluate f(3) - 9
We already found that \[ f(3) = 57 \]So, we subtract 9 from this value: \[ f(3) - 9 = 57 - 9 = 48 \]So, \(f(3) - 9 = 48\).
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Polynomial Functions
A polynomial function is a type of mathematical function that includes terms with non-negative integer exponents of variables. For example, the function given in the exercise is \( f(n) = 5n^2 + 4n \), where \( 5n^2 \) and \( 4n \) are terms. These types of functions are called 'polynomials' because they contain multiple terms added together.
Important features of polynomial functions include:
Important features of polynomial functions include:
- Coefficients: The numerical factors in the terms (e.g., 5 and 4 are the coefficients in the exercise).
- Exponents: The powers to which the variables are raised (e.g., 2 in \( 5n^2 \)).
- Variables: The symbols that represent numbers (e.g., n in \( f(n) \)).
Substitution
Substitution is a fundamental technique in algebra, where you replace a variable with a number or another expression. This method allows you to evaluate functions at specific points.
For example, to find \( f(0) \) from the function \( f(n) = 5n^2 + 4n \), you substitute \( n \) with 0: \( f(0) = 5(0)^2 + 4(0) = 0 \).
Steps for substitution:
For example, to find \( f(0) \) from the function \( f(n) = 5n^2 + 4n \), you substitute \( n \) with 0: \( f(0) = 5(0)^2 + 4(0) = 0 \).
Steps for substitution:
- Identify the variable to substitute.
- Replace the variable in the function with the given number or expression.
- Simplify the expression to arrive at the result.
Algebraic Expressions
An algebraic expression is a combination of variables, numbers, and operations. It's a way to represent mathematical ideas succinctly.
In our example, the function \( f(n) = 5n^2 + 4n \) is an algebraic expression. It contains:
In our example, the function \( f(n) = 5n^2 + 4n \) is an algebraic expression. It contains:
- Variables: n
- Constants: Numbers like 5 and 4
- Operations: Multiplication and addition
Function Notation
Function notation is a way to name a function and its variables in a precise manner. For instance, in the function \( f(n) = 5n^2 + 4n \), \( f \) is the function name, and \( n \) is the variable.
Key points about function notation:
Key points about function notation:
- \( f(n) \) reads as 'f of n,' indicating the function f depending on the variable n.
- Allows us to express how the function behaves differently with distinct inputs, such as \( f(0), f(-1), \) or \( f(3) \).
- Makes it easy to reference and distinguish between multiple functions, like \( f(n) \) and \( g(x) \).