Math Problem Statement

Exercise 4: Let 𝑓 ( π‘₯ )

3 π‘₯ βˆ’ 2 f(x)=3xβˆ’2 and 𝑔 ( π‘₯ )

π‘₯ + 1 2 g(x)= 2 x+1 ​ .

Compute the composition ( 𝑓 ∘ 𝑔 ) ( π‘₯ ) (f∘g)(x). Compute the composition ( 𝑔 ∘ 𝑓 ) ( π‘₯ ) (g∘f)(x).

Solution

To compute the compositions of functions, (f∘g)(x)(f \circ g)(x) and (g∘f)(x)(g \circ f)(x), follow these steps:

1. Given Functions:

  • f(x)=3xβˆ’2f(x) = 3x - 2
  • g(x)=x+12g(x) = \frac{x + 1}{2}

2. Compute (f∘g)(x)(f \circ g)(x):

The composition (f∘g)(x)(f \circ g)(x) means substituting g(x)g(x) into f(x)f(x).

(f∘g)(x)=f(g(x))=f(x+12)(f \circ g)(x) = f(g(x)) = f\left(\frac{x+1}{2}\right)

Substitute x+12\frac{x+1}{2} into f(x)=3xβˆ’2f(x) = 3x - 2:

f(x+12)=3(x+12)βˆ’2f\left(\frac{x+1}{2}\right) = 3\left(\frac{x+1}{2}\right) - 2

Simplify:

f(x+12)=3(x+1)2βˆ’2f\left(\frac{x+1}{2}\right) = \frac{3(x+1)}{2} - 2 f(x+12)=3x+32βˆ’2f\left(\frac{x+1}{2}\right) = \frac{3x + 3}{2} - 2 f(x+12)=3x+32βˆ’42f\left(\frac{x+1}{2}\right) = \frac{3x + 3}{2} - \frac{4}{2} f(x+12)=3xβˆ’12f\left(\frac{x+1}{2}\right) = \frac{3x - 1}{2}

Thus, (f∘g)(x)=3xβˆ’12(f \circ g)(x) = \frac{3x - 1}{2}


3. Compute (g∘f)(x)(g \circ f)(x):

The composition (g∘f)(x)(g \circ f)(x) means substituting f(x)f(x) into g(x)g(x).

(g∘f)(x)=g(f(x))=g(3xβˆ’2)(g \circ f)(x) = g(f(x)) = g(3x - 2)

Substitute 3xβˆ’23x - 2 into g(x)=x+12g(x) = \frac{x+1}{2}:

g(3xβˆ’2)=(3xβˆ’2)+12g(3x - 2) = \frac{(3x - 2) + 1}{2}

Simplify:

g(3xβˆ’2)=3xβˆ’2+12g(3x - 2) = \frac{3x - 2 + 1}{2} g(3xβˆ’2)=3xβˆ’12g(3x - 2) = \frac{3x - 1}{2}

Thus, (g∘f)(x)=3xβˆ’12(g \circ f)(x) = \frac{3x - 1}{2}


Final Results:

  1. (f∘g)(x)=3xβˆ’12(f \circ g)(x) = \frac{3x - 1}{2}
  2. (g∘f)(x)=3xβˆ’12(g \circ f)(x) = \frac{3x - 1}{2}

Observations:

The compositions (f∘g)(x)(f \circ g)(x) and (g∘f)(x)(g \circ f)(x) result in the same expression: 3xβˆ’12\frac{3x - 1}{2}.


Would you like further details or a step-by-step explanation of any part?

Related Questions:

  1. What is the domain of f(x)f(x), g(x)g(x), and their compositions?
  2. How do you compute (f∘f)(x)(f \circ f)(x) or (g∘g)(x)(g \circ g)(x)?
  3. Can ff and gg be inverses of each other? Why or why not?
  4. What is the graphical interpretation of (f∘g)(x)(f \circ g)(x) and (g∘f)(x)(g \circ f)(x)?
  5. How do the compositions change if g(x)=2x+1g(x) = 2x + 1 instead?

Tip:

When dealing with compositions, always substitute the inner function carefully and simplify step by step to avoid errors!

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Math Problem Analysis

Mathematical Concepts

Function Composition
Algebra
Simplification of Expressions

Formulas

f(g(x)) = f(substituted g(x))
g(f(x)) = g(substituted f(x))

Theorems

Composition of Functions

Suitable Grade Level

Grades 9-11