Math Problem Statement

Jika fungsi f(x) = 2x^2 + 5x - 7 dan g(x) = 3x - 12, fungsi (g o f)(-1) adalah?

Solution

To solve the problem:

We are given:

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

We need to find (gf)(1)(g \circ f)(-1), which means g(f(1))g(f(-1)).

Step 1: Compute f(1)f(-1)

Substitute x=1x = -1 into f(x)f(x): f(1)=2(1)2+5(1)7f(-1) = 2(-1)^2 + 5(-1) - 7 f(1)=2(1)57=257=10f(-1) = 2(1) - 5 - 7 = 2 - 5 - 7 = -10

Step 2: Compute g(f(1))=g(10)g(f(-1)) = g(-10)

Substitute x=10x = -10 into g(x)g(x): g(10)=3(10)12g(-10) = 3(-10) - 12 g(10)=3012=42g(-10) = -30 - 12 = -42

Final Answer:

(gf)(1)=42(g \circ f)(-1) = -42

Let me know if you'd like further clarification or have additional questions.


Here are 5 related questions to deepen your understanding:

  1. How do we compute the composite function (fg)(x)(f \circ g)(x), and what is its result in this case?
  2. How would the answer change if f(x)f(x) and g(x)g(x) were switched in composition?
  3. What is the domain of the composite function gf(x)g \circ f(x)?
  4. How can you graphically represent gf(x)g \circ f(x)?
  5. What happens if we set f(x)=g(x)f(x) = g(x) and repeat the problem?

Tip: Always simplify functions step-by-step when working with composite functions

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Math Problem Analysis

Mathematical Concepts

Function Composition
Polynomial Functions

Formulas

f(x) = ax^2 + bx + c (Quadratic Polynomial)
g(x) = mx + b (Linear Function)
(g o f)(x) = g(f(x))

Theorems

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Suitable Grade Level

Grades 9-12