Math Problem Statement

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Kerjakan soal ini dengan benar

Solution

Let's go through each question one by one from the image and solve them accordingly:


1. Given functions f(x)=2x+2f(x) = 2x + 2 and g(x)=x23g(x) = x^2 - 3:

a) Find (fg)(x)(f \circ g)(x) (composition of ff and gg):

  • (fg)(x)(f \circ g)(x) means f(g(x))f(g(x)).

    f(g(x))=f(x23)=2(x23)+2=2x26+2=2x24f(g(x)) = f(x^2 - 3) = 2(x^2 - 3) + 2 = 2x^2 - 6 + 2 = 2x^2 - 4

    So, (fg)(x)=2x24(f \circ g)(x) = 2x^2 - 4.

b) Find (gf)(x)(g \circ f)(x) (composition of gg and ff):

  • (gf)(x)(g \circ f)(x) means g(f(x))g(f(x)).

    g(f(x))=g(2x+2)=(2x+2)23=(4x2+8x+4)3=4x2+8x+1g(f(x)) = g(2x + 2) = (2x + 2)^2 - 3 = (4x^2 + 8x + 4) - 3 = 4x^2 + 8x + 1

    So, (gf)(x)=4x2+8x+1(g \circ f)(x) = 4x^2 + 8x + 1.


2. Explain why (fg)(x)(f \circ g)(x) is not always the same as (gf)(x)(g \circ f)(x), and give an example:

  • The composition of functions depends on the order of operations. When composing ff and gg, the operations performed on xx are different. For example, in (fg)(x)(f \circ g)(x), the function g(x)g(x) is applied first, followed by ff, while in (gf)(x)(g \circ f)(x), f(x)f(x) is applied first.

Example: From question 1, we have:

  • (fg)(x)=2x24(f \circ g)(x) = 2x^2 - 4
  • (gf)(x)=4x2+8x+1(g \circ f)(x) = 4x^2 + 8x + 1

Clearly, 2x244x2+8x+12x^2 - 4 \neq 4x^2 + 8x + 1, so the two compositions are not the same.


3. Given f(x)=2x+3f(x) = 2x + 3 and g(x)=x1g(x) = x - 1, find (fg)1(x)(f \circ g)^{-1}(x) (the inverse of the composition of ff and gg):

  1. First, find (fg)(x)(f \circ g)(x):

    (fg)(x)=f(g(x))=f(x1)=2(x1)+3=2x2+3=2x+1(f \circ g)(x) = f(g(x)) = f(x - 1) = 2(x - 1) + 3 = 2x - 2 + 3 = 2x + 1

  2. Now, find the inverse of fgf \circ g:

    Set y=2x+1y = 2x + 1, and solve for xx: y=2x+1y = 2x + 1 y1=2xy - 1 = 2x x=y12x = \frac{y - 1}{2}

Thus, the inverse is: (fg)1(x)=x12(f \circ g)^{-1}(x) = \frac{x - 1}{2}


4. If f(x)=3x2f(x) = 3x - 2 and (fg)(x)=6x+1(f \circ g)(x) = 6x + 1, find g(x)g(x):

  1. Start by expressing (fg)(x)(f \circ g)(x): (fg)(x)=f(g(x))=3g(x)2(f \circ g)(x) = f(g(x)) = 3g(x) - 2 Given that (fg)(x)=6x+1(f \circ g)(x) = 6x + 1, we have: 3g(x)2=6x+13g(x) - 2 = 6x + 1

  2. Solve for g(x)g(x):

    3g(x)=6x+1+2=6x+33g(x) = 6x + 1 + 2 = 6x + 3 g(x)=6x+33=2x+1g(x) = \frac{6x + 3}{3} = 2x + 1

So, g(x)=2x+1g(x) = 2x + 1.


5. From problem 1, find:

a) (fg)(2)(f \circ g)(2):

Recall from problem 1 that (fg)(x)=2x24(f \circ g)(x) = 2x^2 - 4. Now, substitute x=2x = 2: (fg)(2)=2(22)4=2(4)4=84=4(f \circ g)(2) = 2(2^2) - 4 = 2(4) - 4 = 8 - 4 = 4

b) (gf)(2)(g \circ f)(-2):

Recall from problem 1 that (gf)(x)=4x2+8x+1(g \circ f)(x) = 4x^2 + 8x + 1. Now, substitute x=2x = -2: (gf)(2)=4(2)2+8(2)+1=4(4)16+1=1616+1=1(g \circ f)(-2) = 4(-2)^2 + 8(-2) + 1 = 4(4) - 16 + 1 = 16 - 16 + 1 = 1


Let me know if you need further details or explanations!


Related Questions:

  1. Can you explain the step-by-step process of finding the inverse of a composition of functions?
  2. What are the main conditions for two functions to be inverse to each other?
  3. How does the domain of a composite function differ from that of individual functions?
  4. What are some real-life applications of function compositions?
  5. Can you provide an example where the composition of two functions results in a constant function?

Tip:

When finding the composition of two functions, always apply the second function first and then the first function to avoid errors.

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Math Problem Analysis

Mathematical Concepts

Function composition
Inverse functions
Quadratic functions
Algebra

Formulas

f(g(x))
g(f(x))
(f ∘ g)⁻¹(x)

Theorems

Inverse function theorem
Composition of functions

Suitable Grade Level

High School