Chapter 5: Problem 81
Function Notation Given \(f(x)=x^{2}+x,\) find and simplify the following. a) \(f(a)+f(-a)\) b) \(f(a+h)\) c) \(f(a+h)-f(a)\)
Short Answer
Expert verified
a) 2a^2; b) a^2 + 2ah + h^2 + a + h; c) 2ah + h^2 + h
Step by step solution
01
Expression for f(a)
First, find the expression for \(f(a)\). Substitute \(a\) into \(f(x)\), so \(f(a) = a^2 + a\).
02
Expression for f(-a)
Now, find the expression for \(f(-a)\). Substitute \(-a\) into \(f(x)\), so \(f(-a) = (-a)^2 + (-a) = a^2 - a\).
03
Sum f(a) + f(-a)
Add the expressions determined in the previous steps: \(f(a) + f(-a) = (a^2 + a) + (a^2 - a) = 2a^2\).
04
Expression for f(a+h)
Find the expression for \(f(a+h)\). Substitute \(a+h\) into \(f(x)\), so \(f(a+h) = (a + h)^2 + (a + h)\).
05
Simplify f(a+h)
Expand and simplify the expression for \(f(a+h)\): \(f(a+h) = a^2 + 2ah + h^2 + a + h\).
06
Expression for f(a)
Recall the expression for \(f(a)\): \(f(a) = a^2 + a\).
07
Difference f(a+h) - f(a)
Subtract \(f(a)\) from \(f(a+h)\): \(f(a+h) - f(a) = (a^2 + 2ah + h^2 + a + h) - (a^2 + a)\).
08
Simplify the difference
Simplify the expression: \(f(a+h) - f(a) = a^2 + 2ah + h^2 + a + h - a^2 - a = 2ah + h^2 + h\).
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
function evaluation
Function evaluation is the process of finding the value of a function for a given input. In simpler terms, it means substituting a given number into the function in place of the variable and then calculating the result. For example, if we have a function \(f(x) = x^2 + x\), and we want to find the value of \(f(a)\), we substitute \(a\) for \(x\) in the function, resulting in \(f(a) = a^2 + a\).
Let's see how evaluation works with different values:
Let's see how evaluation works with different values:
- For \(a\): \(f(a) = a^2 + a\)
- For \(-a\): \(f(-a) = (-a)^2 + (-a) = a^2 - a\)
function operations
Function operations involve combining two or more functions in various ways, such as adding, subtracting, multiplying, or dividing them. In this exercise, we focus on addition and subtraction:
Let's combine \(f(a)\) and \(f(-a)\):
For the subtraction operation:
Let's combine \(f(a)\) and \(f(-a)\):
- First, find \(f(a)\) and \(f(-a)\) as we did in the previous section.
- Next, add them: \(f(a) + f(-a) = (a^2 + a) + (a^2 - a) = a^2 + a + a^2 - a = 2a^2\).
For the subtraction operation:
- We find \(f(a+h) - f(a)\).
- This involves substituting \(a+h\) into the function: \(f(a+h) = (a+h)^2 + (a+h) = a^2 + 2ah + h^2 + a + h\).
- Next, subtract \(f(a)\): \(f(a+h) - f(a) = (a^2 + 2ah + h^2 + a + h) - (a^2 + a) = 2ah + h^2 + h\).
simplification
Simplification is the process of reducing a complex expression into a more manageable and understandable form. Let's simplify some expressions step-by-step:
First, let's simplify \(f(a+h)\):
Now let's simplify the difference \(f(a+h) - f(a)\):
Through simplification, we make expressions cleaner and easier to work with, revealing the essential components of the equation.
First, let's simplify \(f(a+h)\):
- Start with its expanded form: \(f(a+h) = (a+h)^2 + (a+h) = a^2 + 2ah + h^2 + a + h\).
- Combine like terms: \(a^2 + a, 2ah, h^2, h\).
Now let's simplify the difference \(f(a+h) - f(a)\):
- Write the expressions: \(f(a+h) = a^2 + 2ah + h^2 + a + h \) and \(f(a) = a^2 + a\).
- Subtract \(f(a)\) from \(f(a+h)\): \(f(a+h) - f(a) = a^2 + 2ah + h^2 + a + h - a^2 - a\).
- Cancel out the common terms: \(a^2 - a^2\) and \(a - a\).
Through simplification, we make expressions cleaner and easier to work with, revealing the essential components of the equation.