Math Problem Statement

For f(x) = x^2 + 4 and g(x) = x^2 - 3, find the following functions: a. (f ◦ g)(x); b. (g ◦ f)(x); c. (f ◦ g)(4); d. (g ◦ f)(4).

Solution

The image contains a mathematical problem related to function composition. Let's break down and solve each part:

Given:

  • f(x)=x2+4f(x) = x^2 + 4
  • g(x)=x23g(x) = x^2 - 3

You are asked to find:

a. (fg)(x)(f \circ g)(x)

This means f(g(x))f(g(x)).

b. (gf)(x)(g \circ f)(x)

This means g(f(x))g(f(x)).

c. (fg)(4)(f \circ g)(4)

This means f(g(4))f(g(4)).

d. (gf)(4)(g \circ f)(4)

This means g(f(4))g(f(4)).

Let's calculate each one step by step.

a. (fg)(x)(f \circ g)(x)

We substitute g(x)g(x) into f(x)f(x): f(g(x))=f(x23)=(x23)2+4f(g(x)) = f(x^2 - 3) = (x^2 - 3)^2 + 4 Now, simplify: (x23)2=x46x2+9(x^2 - 3)^2 = x^4 - 6x^2 + 9 So: f(g(x))=x46x2+9+4=x46x2+13f(g(x)) = x^4 - 6x^2 + 9 + 4 = x^4 - 6x^2 + 13

b. (gf)(x)(g \circ f)(x)

We substitute f(x)f(x) into g(x)g(x): g(f(x))=g(x2+4)=(x2+4)23g(f(x)) = g(x^2 + 4) = (x^2 + 4)^2 - 3 Now, simplify: (x2+4)2=x4+8x2+16(x^2 + 4)^2 = x^4 + 8x^2 + 16 So: g(f(x))=x4+8x2+163=x4+8x2+13g(f(x)) = x^4 + 8x^2 + 16 - 3 = x^4 + 8x^2 + 13

c. (fg)(4)(f \circ g)(4)

First, calculate g(4)g(4): g(4)=423=163=13g(4) = 4^2 - 3 = 16 - 3 = 13 Now, substitute into ff: f(13)=132+4=169+4=173f(13) = 13^2 + 4 = 169 + 4 = 173

d. (gf)(4)(g \circ f)(4)

First, calculate f(4)f(4): f(4)=42+4=16+4=20f(4) = 4^2 + 4 = 16 + 4 = 20 Now, substitute into gg: g(20)=2023=4003=397g(20) = 20^2 - 3 = 400 - 3 = 397

Final Answers:

  • (fg)(x)=x46x2+13(f \circ g)(x) = x^4 - 6x^2 + 13
  • (gf)(x)=x4+8x2+13(g \circ f)(x) = x^4 + 8x^2 + 13
  • (fg)(4)=173(f \circ g)(4) = 173
  • (gf)(4)=397(g \circ f)(4) = 397

Would you like more details on any part of the solution, or do you have any questions?

Here are 5 related questions to extend this topic:

  1. How do you prove the general composition of two functions f(g(x))f(g(x))?
  2. What are some practical applications of function composition?
  3. Can you express fgf \circ g and gfg \circ f graphically?
  4. How do inverses of functions relate to function composition?
  5. How does the order of function composition affect the result?

Tip: Always remember that the order of composition matters—f(g(x))f(g(x)) is generally different from g(f(x))g(f(x)).

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Math Problem Analysis

Mathematical Concepts

Function Composition
Algebra
Polynomial Functions

Formulas

f(x) = x^2 + 4
g(x) = x^2 - 3
(f ◦ g)(x) = f(g(x))
(g ◦ f)(x) = g(f(x))

Theorems

None explicitly stated but involves algebraic manipulation of functions.

Suitable Grade Level

Grades 10-12