Math Problem Statement

Diketahui f(x) = (1 - 5x) / (x + 2), x ≠ -2 dan f⁻¹(x) adalah invers dari f(x). Nilai f⁻¹(-3) = ...

Solution

To solve this problem, let's go through each part carefully.

Given Information

  1. We are given a function: f(x)=15xx+2f(x) = \frac{1 - 5x}{x + 2} with the restriction x2x \neq -2.

  2. We are asked to find the inverse function f1(x)f^{-1}(x) and specifically evaluate f1(3)f^{-1}(-3).

Steps to Find the Inverse Function f1(x)f^{-1}(x)

To find the inverse of f(x)f(x), we'll switch yy and xx and then solve for yy:

  1. Set y=f(x)y = f(x), so: y=15xx+2y = \frac{1 - 5x}{x + 2}

  2. Replace yy with xx and xx with yy (this is to find f1(x)f^{-1}(x)): x=15yy+2x = \frac{1 - 5y}{y + 2}

  3. Multiply both sides by y+2y + 2 to clear the denominator: x(y+2)=15yx(y + 2) = 1 - 5y

  4. Expand and rearrange to solve for yy: xy+2x=15yxy + 2x = 1 - 5y xy+5y=12xxy + 5y = 1 - 2x y(x+5)=12xy(x + 5) = 1 - 2x y=12xx+5y = \frac{1 - 2x}{x + 5}

So, the inverse function is: f1(x)=12xx+5f^{-1}(x) = \frac{1 - 2x}{x + 5}

Finding f1(3)f^{-1}(-3)

Now we substitute x=3x = -3 into f1(x)f^{-1}(x):

f1(3)=12(3)3+5f^{-1}(-3) = \frac{1 - 2(-3)}{-3 + 5}

  1. Simplify the numerator: 12(3)=1+6=71 - 2(-3) = 1 + 6 = 7

  2. Simplify the denominator: 3+5=2-3 + 5 = 2

  3. So, f1(3)=72f^{-1}(-3) = \frac{7}{2}

Answer

The correct answer is: 72\boxed{\frac{7}{2}}

This corresponds to option (e).

Would you like a more detailed explanation or have any questions?

Related Questions

  1. How do we determine the domain and range of an inverse function?
  2. How can we verify if two functions are inverses of each other?
  3. What are the restrictions on a function to ensure it has an inverse?
  4. How can we find inverses for functions with higher degrees, like quadratics?
  5. How does the graphical interpretation of a function and its inverse relate?

Tip

When finding the inverse of a rational function, clear the fraction by multiplying both sides by the denominator first, then isolate terms with yy to solve for it.

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Math Problem Analysis

Mathematical Concepts

Inverse Functions
Rational Functions
Algebra

Formulas

Inverse function formula for rational functions

Theorems

Inverse Function Theorem

Suitable Grade Level

Grades 10-12