Chapter 3: Problem 73
For the following exercises, use each pair of functions to find \(f(g(0))\) and \(g(f(0))\). $$f(x)=5 x+7, g(x)=4-2 x^{2}$$
Short Answer
Expert verified
\( f(g(0)) = 27 \) and \( g(f(0)) = -94 \).
Step by step solution
01
Find g(0)
To find \( f(g(0)) \), we need to evaluate \( g(0) \) first. Substitute \( x = 0 \) into the function \( g(x) \). Thus, \( g(0) = 4 - 2(0)^2 = 4 \).
02
Evaluate f(g(0))
Now that we have \( g(0) = 4 \), substitute this value into the function \( f(x) \). Thus, \( f(g(0)) = f(4) = 5(4) + 7 = 20 + 7 = 27 \).
03
Find f(0)
Next, evaluate \( f(0) \) as required for calculating \( g(f(0)) \). Substitute \( x = 0 \) into the function \( f(x) \). Thus, \( f(0) = 5(0) + 7 = 7 \).
04
Evaluate g(f(0))
Now that we have \( f(0) = 7 \), substitute this value into the function \( g(x) \). Thus, \( g(f(0)) = g(7) = 4 - 2(7)^2 = 4 - 2(49) = 4 - 98 = -94 \).
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Step by Step Solution
Solving a problem step by step can make it less intimidating and help you understand each part thoroughly. Here, we'll tackle the concept of function composition using a step-by-step approach. The goal is to compute specific values such as \( f(g(0)) \) and \( g(f(0)) \) using two given functions.
- Step 1 involves evaluating \( g(0) \). You substitute \( x = 0 \) into \( g(x) = 4 - 2x^2 \). Simplifying gives \( g(0) = 4 \), as \( 2(0)^2 = 0 \).
- In Step 2, we substitute \( g(0) = 4 \) into \( f(x) = 5x + 7 \), resulting in \( f(g(0)) = f(4) = 27 \).
- Next, in Step 3, assess \( f(0) \) by substituting \( x = 0 \) into \( f(x) \), giving \( f(0) = 7 \).
- Finally, Step 4 requires inserting \( f(0) = 7 \) back into \( g(x) \), leading to \( g(f(0)) = g(7) = -94 \).
Evaluating Functions
Evaluating functions is a fundamental skill in algebra and calculus. It involves finding the value of a function given a specific input. Let's break it down using the functions \( f(x) = 5x + 7 \) and \( g(x) = 4 - 2x^2 \).
To evaluate \( g(0) \), replace \( x \) with \( 0 \) in the function \( g \). You compute: \( g(0) = 4 - 2(0)^2 = 4 \).
For \( f(0) \), you substitute \( x = 0 \) into \( f(x) \), obtaining: \( f(0) = 5(0) + 7 = 7 \).Evaluating functions might include:
To evaluate \( g(0) \), replace \( x \) with \( 0 \) in the function \( g \). You compute: \( g(0) = 4 - 2(0)^2 = 4 \).
For \( f(0) \), you substitute \( x = 0 \) into \( f(x) \), obtaining: \( f(0) = 5(0) + 7 = 7 \).Evaluating functions might include:
- Substituting the input value into the function expression.
- Simplifying the mathematical operations to reach a numeric output.
- Checking the result to ensure accuracy in calculation.
Composite Functions
Composite functions involve plugging one function into another. This merger creates a new function that's a combination of existing ones. With \( f(x) = 5x + 7 \) and \( g(x) = 4 - 2x^2 \), our task is to find expressions like \( f(g(x)) \) or \( g(f(x)) \).
For \( f(g(0)) \), we start by evaluating \( g(0) \) to get \( g(0) = 4 \) (from \( g(x) \)) and then \( f(4) \) yields \( 27 \) (using \( f(x) \)).
Meanwhile, \( g(f(0)) \) requires first evaluating \( f(0) \) to reach \( 7 \), then substituting back into \( g(x) \), resulting in \( -94 \). Here's how composite functions work:
For \( f(g(0)) \), we start by evaluating \( g(0) \) to get \( g(0) = 4 \) (from \( g(x) \)) and then \( f(4) \) yields \( 27 \) (using \( f(x) \)).
Meanwhile, \( g(f(0)) \) requires first evaluating \( f(0) \) to reach \( 7 \), then substituting back into \( g(x) \), resulting in \( -94 \). Here's how composite functions work:
- Begin with evaluating the inside function first, which acts like the input to the outside function.
- Take the output from the first evaluation and substitute it into the second function.
- Carry out any simplifications needed to arrive at the final result.