Math Problem Statement

Jika f(x) = 2x^2 + 5x - 7 dan g(x) = 3x - 12, maka nilai (g o f)(2) adalah?

Solution

The problem is asking for the value of (gf)(2)(g \circ f)(2), where the functions f(x)f(x) and g(x)g(x) are defined as follows:

  • f(x)=2x2+5x7f(x) = 2x^2 + 5x - 7
  • g(x)=3x12g(x) = 3x - 12

To solve for (gf)(2)(g \circ f)(2), which is the composition of functions, we proceed with the following steps:

Step 1: Calculate f(2)f(2)

Substitute x=2x = 2 into the function f(x)f(x): f(2)=2(2)2+5(2)7f(2) = 2(2)^2 + 5(2) - 7 f(2)=2(4)+107=8+107=11f(2) = 2(4) + 10 - 7 = 8 + 10 - 7 = 11

Step 2: Calculate g(f(2))=g(11)g(f(2)) = g(11)

Now, substitute f(2)=11f(2) = 11 into the function g(x)g(x): g(11)=3(11)12g(11) = 3(11) - 12 g(11)=3312=21g(11) = 33 - 12 = 21

Thus, (gf)(2)=21(g \circ f)(2) = 21.

The correct answer is B. 21.

Would you like further details on any steps? Here are five related questions for practice:

  1. What is (fg)(2)(f \circ g)(2)?
  2. How do you find the domain of a composite function?
  3. If g(x)=x31g(x) = x^3 - 1, what is (gf)(2)(g \circ f)(2) for the same f(x)f(x)?
  4. How would the answer change if f(x)f(x) were a linear function?
  5. How can you verify the result of a composite function graphically?

Tip: When dealing with composite functions, always evaluate the inner function first and then apply the result to the outer function.

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Math Problem Analysis

Mathematical Concepts

Composition of Functions
Algebra

Formulas

f(x) = 2x^2 + 5x - 7
g(x) = 3x - 12
g(f(x))

Theorems

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Suitable Grade Level

Grades 10-12