Math Problem Statement

Jika hasil refleksi dari fungsi linear f(x) = -1/2x + 8 terhadap garis y = -x adalah g(x), tentukan nilai g(4)!

Solution

The problem asks for the reflection of the linear function f(x)=12x+8f(x) = -\frac{1}{2}x + 8 with respect to the line y=xy = -x, and it requires determining g(4)g(4), where g(x)g(x) is the reflected function.

Step-by-step Solution:

  1. Find the reflection rules: When a function is reflected over the line y=xy = -x, the coordinates (x,y)(x, y) transform as follows:

    • The new coordinates after reflection are (y,x)(y, x). In terms of functions, this means the reflection of f(x)f(x) across the line y=xy = -x can be written as: g(x)=f1(x)g(x) = f^{-1}(-x)
    • So, to find the reflection, we need to first find the inverse of f(x)f(x).
  2. Find the inverse of f(x)f(x):
    The given function is f(x)=12x+8f(x) = -\frac{1}{2}x + 8. To find the inverse:

    • Set y=12x+8y = -\frac{1}{2}x + 8.
    • Solve for xx: y=12x+8y = -\frac{1}{2}x + 8 y8=12xy - 8 = -\frac{1}{2}x x=2(y8)=2y+16x = -2(y - 8) = -2y + 16 Therefore, the inverse function is: f1(x)=2x+16f^{-1}(x) = -2x + 16
  3. Find g(x)=f1(x)g(x) = f^{-1}(-x):
    Substitute x-x into the inverse function: g(x)=f1(x)=2(x)+16=2x+16g(x) = f^{-1}(-x) = -2(-x) + 16 = 2x + 16

  4. Calculate g(4)g(4): Now, substitute x=4x = 4 into g(x)g(x): g(4)=2(4)+16=8+16=24g(4) = 2(4) + 16 = 8 + 16 = 24

Thus, the value of g(4)g(4) is 24.


Would you like more details on any step or have further questions?

Here are five related questions for you to explore:

  1. How do you find the reflection of a linear function over other lines like y=xy = x?
  2. What is the geometric meaning of reflecting a function over the line y=xy = -x?
  3. How do you find the inverse of a more complex function, such as a quadratic?
  4. What are the properties of functions and their inverses in terms of domain and range?
  5. Can the reflection of a non-linear function, such as f(x)=x2f(x) = x^2, also be calculated similarly?

Tip: Always ensure that the function is one-to-one before finding its inverse. If a function is not one-to-one, you may need to restrict its domain.

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Math Problem Analysis

Mathematical Concepts

Linear Function
Reflection
Inverse Function

Formulas

Reflection across y = -x: g(x) = f^{-1}(-x)
Inverse of f(x): f^{-1}(x)

Theorems

Inverse Function Theorem

Suitable Grade Level

Grades 10-12