Math Problem Statement

The graphs of f(x) = y and g(x) = y are given below. What is the value of (g o f)(x) and (f o g)(x)?

Solution

The problem asks about the composition of two functions, f(x)f(x) and g(x)g(x), whose graphs are given in the image. Let's break down how to solve the two parts of the question.

The composition of functions, such as (gf)(x)(g \circ f)(x), means that you first apply the function f(x)f(x), and then apply the function g(x)g(x) to the result.

1. Part (a): (gf)(x)(g \circ f)(x)

This is calculated as:

(gf)(x)=g(f(x))(g \circ f)(x) = g(f(x))

You first find f(x)f(x) from the graph of ff, and then use that value to find g(f(x))g(f(x)) from the graph of gg.

Let's solve it step-by-step for different values of xx:

x=1x = 1:

  • From the graph of f(x)f(x), f(1)=1f(1) = 1.
  • Now, use this value in the graph of gg. g(1)=3g(1) = 3.
  • Therefore, (gf)(1)=g(f(1))=3(g \circ f)(1) = g(f(1)) = 3.

x=2x = 2:

  • From the graph of f(x)f(x), f(2)=2f(2) = 2.
  • Now, g(2)=4g(2) = 4.
  • Therefore, (gf)(2)=g(f(2))=4(g \circ f)(2) = g(f(2)) = 4.

x=3x = 3:

  • From the graph of f(x)f(x), f(3)=1f(3) = 1.
  • Now, g(1)=3g(1) = 3 (as before).
  • Therefore, (gf)(3)=g(f(3))=3(g \circ f)(3) = g(f(3)) = 3.

x=4x = 4:

  • From the graph of f(x)f(x), f(4)=4f(4) = 4.
  • Now, g(4)=2g(4) = 2.
  • Therefore, (gf)(4)=g(f(4))=2(g \circ f)(4) = g(f(4)) = 2.

So the values for (gf)(x)(g \circ f)(x) are: (gf)(1)=3,(gf)(2)=4,(gf)(3)=3,(gf)(4)=2.(g \circ f)(1) = 3, \quad (g \circ f)(2) = 4, \quad (g \circ f)(3) = 3, \quad (g \circ f)(4) = 2.

2. Part (b): (fg)(x)(f \circ g)(x)

This is calculated as:

(fg)(x)=f(g(x))(f \circ g)(x) = f(g(x))

Now, we will use g(x)g(x) first and then apply f(x)f(x).

x=1x = 1:

  • From the graph of g(x)g(x), g(1)=3g(1) = 3.
  • Now, from the graph of f(x)f(x), f(3)=1f(3) = 1.
  • Therefore, (fg)(1)=f(g(1))=1(f \circ g)(1) = f(g(1)) = 1.

x=2x = 2:

  • From the graph of g(x)g(x), g(2)=4g(2) = 4.
  • Now, f(4)=4f(4) = 4.
  • Therefore, (fg)(2)=f(g(2))=4(f \circ g)(2) = f(g(2)) = 4.

x=3x = 3:

  • From the graph of g(x)g(x), g(3)=2g(3) = 2.
  • Now, f(2)=2f(2) = 2.
  • Therefore, (fg)(3)=f(g(3))=2(f \circ g)(3) = f(g(3)) = 2.

x=4x = 4:

  • From the graph of g(x)g(x), g(4)=1g(4) = 1.
  • Now, f(1)=1f(1) = 1.
  • Therefore, (fg)(4)=f(g(4))=1(f \circ g)(4) = f(g(4)) = 1.

So the values for (fg)(x)(f \circ g)(x) are: (fg)(1)=1,(fg)(2)=4,(fg)(3)=2,(fg)(4)=1.(f \circ g)(1) = 1, \quad (f \circ g)(2) = 4, \quad (f \circ g)(3) = 2, \quad (f \circ g)(4) = 1.

Would you like more details on any of the steps? Here are some related questions for further practice:

  1. What is the value of (ff)(x)(f \circ f)(x) for different values of xx?
  2. What is the value of (gg)(x)(g \circ g)(x)?
  3. How would you find the inverse of f(x)f(x) and g(x)g(x) based on the graphs?
  4. Can you generalize a formula for (gf)(x)(g \circ f)(x) if f(x)f(x) and g(x)g(x) are given as functions?
  5. What is the domain and range of (gf)(x)(g \circ f)(x) and (fg)(x)(f \circ g)(x)?

Tip: When working with function compositions, it's helpful to break down each step and focus on applying one function at a time.

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Math Problem Analysis

Mathematical Concepts

Function Composition
Graphs of Functions

Formulas

(g o f)(x) = g(f(x))
(f o g)(x) = f(g(x))

Theorems

Composition of Functions Theorem

Suitable Grade Level

High School, Grades 9-12