Math Problem Statement

Kerjakan soal nomor 4

Diketahui 4f(x) + 2f(-x) = 5x + 3 dengan f(x) merupakan fungsi linear. Berdasarkan informasi tersebut, manakah di antara pilihan berikut yang bernilai benar? 1. f(1) = -3 2. f^{-1}(8) = 3 3. f(-3) = 1 4. f^{-1}(-2) = -1

Solution

Let's analyze the problem and solve it.

The given equation is: 4f(x)+2f(x)=5x+34f(x) + 2f(-x) = 5x + 3 where f(x)f(x) is a linear function.

  1. We know that a linear function can be written as f(x)=ax+bf(x) = ax + b, where aa and bb are constants.

  2. Let’s substitute f(x)=ax+bf(x) = ax + b and f(x)=ax+bf(-x) = -ax + b into the equation: 4(ax+b)+2(ax+b)=5x+34(ax + b) + 2(-ax + b) = 5x + 3 Expanding both sides: 4(ax+b)=4ax+4b4(ax + b) = 4ax + 4b 2(ax+b)=2ax+2b2(-ax + b) = -2ax + 2b Now combine the terms: (4ax2ax)+(4b+2b)=5x+3(4ax - 2ax) + (4b + 2b) = 5x + 3 Simplify: 2ax+6b=5x+32ax + 6b = 5x + 3 By comparing the coefficients of xx and the constants, we get: 2a=5and6b=32a = 5 \quad \text{and} \quad 6b = 3 Solving these equations: a=52,b=12a = \frac{5}{2}, \quad b = \frac{1}{2}

Thus, the function is: f(x)=52x+12f(x) = \frac{5}{2}x + \frac{1}{2}

Now, let's check the statements:

  1. f(1)=3f(1) = -3: f(1)=52(1)+12=52+12=3(not 3)f(1) = \frac{5}{2}(1) + \frac{1}{2} = \frac{5}{2} + \frac{1}{2} = 3 \quad (\text{not } -3) False

  2. f1(8)=3f^{-1}(8) = 3: To find the inverse of f(x)=52x+12f(x) = \frac{5}{2}x + \frac{1}{2}, we solve for xx: y=52x+12y = \frac{5}{2}x + \frac{1}{2} Solve for xx: 2y=5x+15x=2y1x=2y152y = 5x + 1 \quad \Rightarrow \quad 5x = 2y - 1 \quad \Rightarrow \quad x = \frac{2y - 1}{5} The inverse function is: f1(y)=2y15f^{-1}(y) = \frac{2y - 1}{5} Now, substitute y=8y = 8: f1(8)=2(8)15=1615=155=3f^{-1}(8) = \frac{2(8) - 1}{5} = \frac{16 - 1}{5} = \frac{15}{5} = 3 True

  3. f(3)=1f(-3) = 1: f(3)=52(3)+12=152+12=142=7f(-3) = \frac{5}{2}(-3) + \frac{1}{2} = -\frac{15}{2} + \frac{1}{2} = -\frac{14}{2} = -7 False

  4. f1(2)=1f^{-1}(-2) = -1: Substitute y=2y = -2 into the inverse function: f1(2)=2(2)15=415=55=1f^{-1}(-2) = \frac{2(-2) - 1}{5} = \frac{-4 - 1}{5} = \frac{-5}{5} = -1 True

Conclusion:

Statements 2 and 4 are true. Therefore, the correct answer is C: 2 and 4 SAJA yang benar.

Would you like any further details or clarifications? Here are five related questions:

  1. How is the inverse function of a linear function generally derived?
  2. What does it mean for a function to be linear?
  3. What is the significance of the slope aa in the linear function f(x)=ax+bf(x) = ax + b?
  4. How does the inverse function reflect the original function graphically?
  5. How can you verify if a function has an inverse?

Tip: Always check the inverse function by plugging the result back into the original function.

Ask a new question for Free

By Image

Drop file here or Click Here to upload

Math Problem Analysis

Mathematical Concepts

Linear Functions
Inverse Functions
Algebra

Formulas

Linear function form: f(x) = ax + b
Inverse function formula: f^{-1}(x)
Solving equations involving linear functions

Theorems

Properties of linear functions
Inverse function theorem

Suitable Grade Level

Grades 10-12