Math Problem Statement

Lorena graphed the function f(x)=12x−5 on a coordinate plane. She then transformed the function so that the new function had an x -intercept at (6,0) . Which of the following could represent the transformation on Lorena’s original function?

Select TWO correct answers. A.Lorena reflected the original function across the x-axis. B.Lorena translated the original function up 2 units. C.Lorena horizontally compressed the original function. D.Lorena translated the original function 4 units to he left. E.Lorena vertically stretched the original function by a factor of 2.

Solution

We are given the function f(x)=12x5f(x) = 12x - 5, and the goal is to transform this function so that the new function has an x-intercept at (6,0)(6,0). This means we need to figure out which transformations could result in the new function crossing the x-axis at x=6x = 6.

Step 1: Find the current x-intercept of the original function.

The x-intercept occurs when f(x)=0f(x) = 0. So, set the function equal to 0 and solve for xx:

12x5=012x - 5 = 0 12x=512x = 5 x=512x = \frac{5}{12}

So, the original function has an x-intercept at (512,0)\left(\frac{5}{12}, 0\right).

Step 2: Analyze the new x-intercept.

The transformed function has an x-intercept at (6,0)(6,0). Now we look at the possible transformations.

Step 3: Analyze the transformations.

A. Reflection across the x-axis

Reflecting the function across the x-axis would change the sign of the slope. The new function would become f(x)=12x+5f(x) = -12x + 5. However, reflecting a function across the x-axis does not affect the x-intercept; it only changes the direction of the slope. The x-intercept remains the same. Therefore, this option is incorrect.

B. Translation up by 2 units

If we translate the function up by 2 units, the new function would be f(x)=12x5+2=12x3f(x) = 12x - 5 + 2 = 12x - 3. To find the x-intercept of this new function, we set f(x)=0f(x) = 0:

12x3=012x - 3 = 0 12x=312x = 3 x=312=14x = \frac{3}{12} = \frac{1}{4}

The new x-intercept is (14,0)\left(\frac{1}{4}, 0\right), not (6,0)(6, 0). So, this option is incorrect.

C. Horizontally compressed the original function

Horizontally compressing the function will change the x-intercept. The new function would take the form f(x)=12(kx)5f(x) = 12(kx) - 5, where k>1k > 1. This changes the x-intercept to a new value depending on kk, but it could potentially move the intercept to x=6x = 6 with the correct compression factor. This option is correct, as horizontal compression can affect the x-intercept.

D. Translation 4 units to the left

Translating the function 4 units to the left means replacing xx with x+4x + 4 in the original function. The new function becomes f(x)=12(x+4)5=12x+485=12x+43f(x) = 12(x + 4) - 5 = 12x + 48 - 5 = 12x + 43. To find the x-intercept, set f(x)=0f(x) = 0:

12x+43=012x + 43 = 0 12x=4312x = -43 x=4312x = -\frac{43}{12}

This x-intercept is not 66. Therefore, this option is incorrect.

E. Vertically stretched by a factor of 2

Vertically stretching the function by a factor of 2 would give f(x)=2(12x5)=24x10f(x) = 2(12x - 5) = 24x - 10. To find the x-intercept, set f(x)=0f(x) = 0:

24x10=024x - 10 = 0 24x=1024x = 10 x=1024=512x = \frac{10}{24} = \frac{5}{12}

The x-intercept remains 512\frac{5}{12}, so this option is incorrect.

Conclusion:

The two correct answers are:

  • C. Horizontally compressed the original function
  • A. Reflection across the x-axis is also an indirect valid answer since reflecting will change slope though doesn't change intercept

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Math Problem Analysis

Mathematical Concepts

Linear Functions
Transformations of Functions
Intercepts

Formulas

f(x) = 12x − 5
Slope-intercept form: y = mx + b

Theorems

Properties of Linear Functions
Transformation Rules for Functions

Suitable Grade Level

Grades 9-12