Math Problem Statement

give me step by step answer in detail from the beginning

Fungsi f: R → R dan g: R → R dirumuskan dengan g(x) = 3x^2 - 3x - 1 dan f(x) = 4x - 6, maka (gof)^-1(x) = ...

Solution

The problem in the image asks to find (gf)1(x)(g \circ f)^{-1}(x), where the functions g(x)g(x) and f(x)f(x) are defined as follows:

  • g(x)=3x23x1g(x) = 3x^2 - 3x - 1
  • f(x)=4x6f(x) = 4x - 6

The composition (gf)(x)(g \circ f)(x) means g(f(x))g(f(x)), and the task is to find the inverse of this composition, (gf)1(x)(g \circ f)^{-1}(x).

Step-by-Step Solution:

Step 1: Find the composition (gf)(x)=g(f(x))(g \circ f)(x) = g(f(x))

Substitute f(x)=4x6f(x) = 4x - 6 into the function g(x)=3x23x1g(x) = 3x^2 - 3x - 1.

g(f(x))=g(4x6)g(f(x)) = g(4x - 6)

Substitute 4x64x - 6 into the formula for g(x)g(x):

g(4x6)=3(4x6)23(4x6)1g(4x - 6) = 3(4x - 6)^2 - 3(4x - 6) - 1

Step 2: Simplify g(4x6)g(4x - 6)

First, calculate (4x6)2(4x - 6)^2:

(4x6)2=(4x)22(4x)(6)+62=16x248x+36(4x - 6)^2 = (4x)^2 - 2(4x)(6) + 6^2 = 16x^2 - 48x + 36

Now substitute this into the equation for g(f(x))g(f(x)):

g(f(x))=3(16x248x+36)3(4x6)1g(f(x)) = 3(16x^2 - 48x + 36) - 3(4x - 6) - 1

Simplify the terms:

g(f(x))=48x2144x+10812x+181g(f(x)) = 48x^2 - 144x + 108 - 12x + 18 - 1

Combine like terms:

g(f(x))=48x2156x+125g(f(x)) = 48x^2 - 156x + 125

Thus, (gf)(x)=48x2156x+125(g \circ f)(x) = 48x^2 - 156x + 125.

Step 3: Find the inverse of (gf)(x)(g \circ f)(x)

Now, to find the inverse, we need to solve for xx in terms of yy, where y=48x2156x+125y = 48x^2 - 156x + 125.

Start by setting y=48x2156x+125y = 48x^2 - 156x + 125:

y=48x2156x+125y = 48x^2 - 156x + 125

Step 4: Solve the quadratic equation

To solve for xx, we will use the quadratic formula:

x=b±b24ac2ax = \frac{-b \pm \sqrt{b^2 - 4ac}}{2a}

For the quadratic equation 48x2156x+(125y)=048x^2 - 156x + (125 - y) = 0, the coefficients are:

  • a=48a = 48
  • b=156b = -156
  • c=125yc = 125 - y

Substitute these values into the quadratic formula:

x=(156)±(156)24(48)(125y)2(48)x = \frac{-(-156) \pm \sqrt{(-156)^2 - 4(48)(125 - y)}}{2(48)}

Simplify the discriminant:

x=156±2433619200+192y96x = \frac{156 \pm \sqrt{24336 - 19200 + 192y}}{96}

x=156±4136+192y96x = \frac{156 \pm \sqrt{4136 + 192y}}{96}

Thus, the inverse function (gf)1(x)(g \circ f)^{-1}(x) is:

(gf)1(x)=156±4136+192x96(g \circ f)^{-1}(x) = \frac{156 \pm \sqrt{4136 + 192x}}{96}

Final Answer:

(gf)1(x)=156±4136+192x96(g \circ f)^{-1}(x) = \frac{156 \pm \sqrt{4136 + 192x}}{96}

This is the inverse of the composition (gf)(x)(g \circ f)(x).


Would you like further details or clarifications on any part of this solution?

Here are some related questions you could explore:

  1. What is the domain of (gf)(x)(g \circ f)(x)?
  2. How do you verify if two functions are inverses of each other?
  3. What is the graphical interpretation of inverse functions?
  4. How do you find the inverse of a function without using the quadratic formula?
  5. Can you find the inverse of the individual functions f(x)f(x) and g(x)g(x)?

Tip: When solving for the inverse of a function, remember to swap xx and yy, and then solve for yy, which becomes your inverse function.

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Math Problem Analysis

Mathematical Concepts

Function Composition
Inverse Function
Quadratic Equations

Formulas

(g ∘ f)(x) = g(f(x))
Quadratic formula: x = (-b ± √(b² - 4ac)) / 2a

Theorems

Quadratic formula

Suitable Grade Level

High School (Grades 10-12)