Math Problem Statement

Tentukan persamaan bayangan dari fungsi f(x) = x^2 - 4x + 3 jika di refleksikan terhadap: a. Garis x = -3, b. Garis y = -3

Solution

The problem asks for the reflection of the function f(x)=x24x+3f(x) = x^2 - 4x + 3 with respect to:

a. The line x=3x = -3

b. The line y=3y = -3

Let's break it down step by step:

a. Reflection with respect to x=3x = -3:

To reflect a function across a vertical line like x=3x = -3, we replace xx in the function with (x+3)-(x + 3). The reflection rule for vertical lines is x=(x+c)x' = -(x + c) where cc is the xx-coordinate of the vertical line (here c=3c = -3).

  1. Start with the original function f(x)=x24x+3f(x) = x^2 - 4x + 3.
  2. Replace xx with (x+3)-(x + 3) to reflect across x=3x = -3:

f(x3)=(x3)24(x3)+3f(-x - 3) = (-x - 3)^2 - 4(-x - 3) + 3

Now, let's simplify this:

=(x2+6x+9)+4(x+3)+3= (x^2 + 6x + 9) + 4(x + 3) + 3 =x2+6x+9+4x+12+3= x^2 + 6x + 9 + 4x + 12 + 3 =x2+10x+24= x^2 + 10x + 24

So, the reflection of the function across x=3x = -3 is f(x)=x2+10x+24f(x) = x^2 + 10x + 24.

b. Reflection with respect to y=3y = -3:

To reflect a function across a horizontal line like y=3y = -3, we apply the following rule: the reflection is f(x)=f(x)6f'(x) = -f(x) - 6, where 6 comes from doubling the distance between the function's original vertex and the line of reflection (since the line is at y=3y = -3).

  1. The original function is f(x)=x24x+3f(x) = x^2 - 4x + 3.
  2. To reflect across y=3y = -3, we first negate the function and subtract 6:

f(x)=(x24x+3)6f'(x) = -(x^2 - 4x + 3) - 6 =x2+4x36= -x^2 + 4x - 3 - 6 =x2+4x9= -x^2 + 4x - 9

So, the reflection of the function across y=3y = -3 is f(x)=x2+4x9f(x) = -x^2 + 4x - 9.


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

Here are 5 related questions to consider:

  1. How do you reflect a function across the y-axis?
  2. What happens to the vertex of a parabola during reflection over a line?
  3. How can you find the vertex of a quadratic function?
  4. What is the general rule for reflecting a graph across a vertical line?
  5. How can transformations affect the symmetry of a function?

Tip: Always double-check the signs when reflecting functions to avoid calculation mistakes!

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Math Problem Analysis

Mathematical Concepts

Function Reflection
Quadratic Function

Formulas

Reflection over vertical line x = -c: Replace x with -(x + c)
Reflection over horizontal line y = -c: Apply f'(x) = -f(x) - 2c

Theorems

Reflection Theorem: A function f(x) can be reflected over a vertical or horizontal line using transformation rules

Suitable Grade Level

Grades 10-12