Math Problem Statement

  1. Suppose f(x) = x+2 , g(x) = x−2, and h(x) = 3x for x ∈ R} , where R is the set of real numbers. Find (g ◦ f) , (f ◦ g), (f ◦ f) and (g ◦ g). detiled

Solution

To solve for the compositions of the functions f(x)=x+2f(x) = x + 2, g(x)=x2g(x) = x - 2, and h(x)=3xh(x) = 3x, let's work step by step through each composition. We'll use the definition of composition of functions: (gf)(x)=g(f(x))(g \circ f)(x) = g(f(x)), (fg)(x)=f(g(x))(f \circ g)(x) = f(g(x)), and so on.

1. Find (gf)(x)=g(f(x))(g \circ f)(x) = g(f(x)):

Substitute f(x)=x+2f(x) = x + 2 into g(x)=x2g(x) = x - 2:

g(f(x))=g(x+2)g(f(x)) = g(x + 2)

Since g(x)=x2g(x) = x - 2, replace xx with x+2x + 2:

g(x+2)=(x+2)2=xg(x + 2) = (x + 2) - 2 = x

Thus, (gf)(x)=x(g \circ f)(x) = x.


2. Find (fg)(x)=f(g(x))(f \circ g)(x) = f(g(x)):

Substitute g(x)=x2g(x) = x - 2 into f(x)=x+2f(x) = x + 2:

f(g(x))=f(x2)f(g(x)) = f(x - 2)

Since f(x)=x+2f(x) = x + 2, replace xx with x2x - 2:

f(x2)=(x2)+2=xf(x - 2) = (x - 2) + 2 = x

Thus, (fg)(x)=x(f \circ g)(x) = x.


3. Find (ff)(x)=f(f(x))(f \circ f)(x) = f(f(x)):

Substitute f(x)=x+2f(x) = x + 2 into itself:

f(f(x))=f(x+2)f(f(x)) = f(x + 2)

Since f(x)=x+2f(x) = x + 2, replace xx with x+2x + 2:

f(x+2)=(x+2)+2=x+4f(x + 2) = (x + 2) + 2 = x + 4

Thus, (ff)(x)=x+4(f \circ f)(x) = x + 4.


4. Find (gg)(x)=g(g(x))(g \circ g)(x) = g(g(x)):

Substitute g(x)=x2g(x) = x - 2 into itself:

g(g(x))=g(x2)g(g(x)) = g(x - 2)

Since g(x)=x2g(x) = x - 2, replace xx with x2x - 2:

g(x2)=(x2)2=x4g(x - 2) = (x - 2) - 2 = x - 4

Thus, (gg)(x)=x4(g \circ g)(x) = x - 4.


Final Results:

  1. (gf)(x)=x(g \circ f)(x) = x
  2. (fg)(x)=x(f \circ g)(x) = x
  3. (ff)(x)=x+4(f \circ f)(x) = x + 4
  4. (gg)(x)=x4(g \circ g)(x) = x - 4

Would you like to explore these results further or analyze another example?

Related Questions:

  1. What happens if we calculate (hf)(h \circ f) or (hg)(h \circ g)?
  2. What is the geometric interpretation of (fg)(x)(f \circ g)(x) and (gf)(x)(g \circ f)(x)?
  3. How do the compositions fff \circ f and ggg \circ g behave for specific values of xx?
  4. What would happen if we introduced a new function k(x)=x2k(x) = x^2?
  5. How does function composition relate to inverses of functions?

Tip:

When working with compositions, always substitute step by step to avoid errors. Check whether the functions simplify to identities or create new transformations.

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Math Problem Analysis

Mathematical Concepts

Function Composition
Algebra
Real Numbers

Formulas

(g ◦ f)(x) = g(f(x))
(f ◦ g)(x) = f(g(x))
(f ◦ f)(x) = f(f(x))
(g ◦ g)(x) = g(g(x))

Theorems

Composition of Functions

Suitable Grade Level

Grades 9-12