Math Problem Statement

Let f(x)=4x+4 and g(x)=2x2+4x. Then (f∘g)(2)= , (f∘g)(x)= .

Solution

We are given two functions f(x)=4x+4f(x) = 4x + 4 and g(x)=2x2+4xg(x) = 2x^2 + 4x. We need to find:

  1. (fg)(2)(f \circ g)(2), which means applying g(x)g(x) first and then f(x)f(x) to the result.
  2. (fg)(x)(f \circ g)(x), the general composition of f(x)f(x) and g(x)g(x).

Step 1: Finding (fg)(2)(f \circ g)(2)

The notation (fg)(2)(f \circ g)(2) means f(g(2))f(g(2)). So we first calculate g(2)g(2), then apply ff to that result.

g(x)=2x2+4xg(x) = 2x^2 + 4x Substitute x=2x = 2: g(2)=2(2)2+4(2)=2(4)+8=8+8=16g(2) = 2(2)^2 + 4(2) = 2(4) + 8 = 8 + 8 = 16

Now apply ff to g(2)g(2): f(x)=4x+4f(x) = 4x + 4 Substitute x=16x = 16: f(16)=4(16)+4=64+4=68f(16) = 4(16) + 4 = 64 + 4 = 68

Thus, (fg)(2)=68(f \circ g)(2) = 68.

Step 2: Finding (fg)(x)(f \circ g)(x)

The general form (fg)(x)(f \circ g)(x) means f(g(x))f(g(x)), so we substitute g(x)g(x) into f(x)f(x).

f(x)=4x+4f(x) = 4x + 4 Substitute g(x)=2x2+4xg(x) = 2x^2 + 4x into f(x)f(x): f(g(x))=4(2x2+4x)+4f(g(x)) = 4(2x^2 + 4x) + 4 Distribute the 4: f(g(x))=8x2+16x+4f(g(x)) = 8x^2 + 16x + 4

Thus, (fg)(x)=8x2+16x+4(f \circ g)(x) = 8x^2 + 16x + 4.

Final Answers:

  1. (fg)(2)=68(f \circ g)(2) = 68
  2. (fg)(x)=8x2+16x+4(f \circ g)(x) = 8x^2 + 16x + 4

Would you like further details or explanations?

Here are 5 related questions:

  1. What is the result of (gf)(2)(g \circ f)(2)?
  2. What is (gf)(x)(g \circ f)(x)?
  3. How would the composition change if f(x)=5x+3f(x) = 5x + 3?
  4. What is the derivative of (fg)(x)(f \circ g)(x)?
  5. Can you compute (ff)(x)(f \circ f)(x)?

Tip: When solving compositions of functions, always apply the innermost function first, then the outer function.

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Math Problem Analysis

Mathematical Concepts

Function Composition
Quadratic Functions

Formulas

f(x) = 4x + 4
g(x) = 2x^2 + 4x
(f∘g)(x) = f(g(x))

Theorems

Composition of Functions

Suitable Grade Level

Grades 9-11