Math Problem Statement

Let f(x) = -3x - 1 and g(x) = x^2 + 5. Find (f ∘ g)(-6).

Solution

We are given two functions:

f(x)=3x1f(x) = -3x - 1 g(x)=x2+5g(x) = x^2 + 5

We are asked to find (fg)(6)(f \circ g)(-6), which means evaluating the composite function f(g(6))f(g(-6)).

Step 1: Evaluate g(6)g(-6)

g(x)=x2+5g(x) = x^2 + 5 Substitute x=6x = -6: g(6)=(6)2+5=36+5=41g(-6) = (-6)^2 + 5 = 36 + 5 = 41

Step 2: Evaluate f(g(6))=f(41)f(g(-6)) = f(41)

f(x)=3x1f(x) = -3x - 1 Substitute x=41x = 41: f(41)=3(41)1=1231=124f(41) = -3(41) - 1 = -123 - 1 = -124

Thus, (fg)(6)=124(f \circ g)(-6) = -124.

Let me know if you need further clarifications!

Follow-up Questions:

  1. What is the general form of a composite function?
  2. How would you reverse this process to solve for (gf)(6)(g \circ f)(-6)?
  3. How does the chain rule in calculus relate to composite functions?
  4. What happens if we change the functions f(x)f(x) or g(x)g(x)?
  5. How do you find the domain of a composite function?

Tip: Always start by evaluating the innermost function first when working with composite functions.

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Math Problem Analysis

Mathematical Concepts

Algebra
Composite Functions

Formulas

f(x) = -3x - 1
g(x) = x^2 + 5

Theorems

Composite Function Evaluation

Suitable Grade Level

Grades 9-12