Math Problem Statement

Find \((f \circ g)(-2)\) for the following functions: \( f(x) = x^3 + x^2 \) and \( g(x) = x^3 - 4 \).

Solution

To solve this problem, we need to evaluate the combined function (fg)(2)(f \circ g)(-2) for the given functions f(x)=x3+x2f(x) = x^3 + x^2 and g(x)=x34g(x) = x^3 - 4.

Step-by-Step Solution

  1. Evaluate g(2)g(-2): Substitute x=2x = -2 into g(x)=x34g(x) = x^3 - 4: g(2)=(2)34=84=12g(-2) = (-2)^3 - 4 = -8 - 4 = -12 So, g(2)=12g(-2) = -12.

  2. Evaluate f(g(2))=f(12)f(g(-2)) = f(-12): Now we need to substitute x=12x = -12 into f(x)=x3+x2f(x) = x^3 + x^2: f(12)=(12)3+(12)2f(-12) = (-12)^3 + (-12)^2 Calculate each term separately:

    • (12)3=1728(-12)^3 = -1728
    • (12)2=144(-12)^2 = 144

    Therefore, f(12)=1728+144=1584f(-12) = -1728 + 144 = -1584

Final Answer

(fg)(2)=1584(f \circ g)(-2) = -1584

Let me know if you'd like more details or have any questions!


Here are five related questions for further practice:

  1. How would you evaluate (gf)(2)(g \circ f)(-2) for the same functions?
  2. What is (fg)(1)(f \circ g)(1) for the given functions?
  3. How would you approach finding (fg)(0)(f \circ g)(0)?
  4. If h(x)=x2+3xh(x) = x^2 + 3x, how would you calculate (fh)(2)(f \circ h)(2)?
  5. What does it mean for a function to be "one-to-one," and how does this apply to f(x)f(x) or g(x)g(x)?

Tip: When working with composition of functions, always start by evaluating the innermost function first, then substitute its result into the outer function.

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Math Problem Analysis

Mathematical Concepts

Function Composition
Polynomial Functions
Exponents

Formulas

\((f \circ g)(x) = f(g(x))\)
Exponential expressions \(a^n\)

Theorems

Definition of Function Composition

Suitable Grade Level

Grades 10-12