Find the Linear Function with Slope ±2 and Domain x > 3

Question

The following is a function that is positive in domain:

3 < x

Choose the equation that describes it given that the absolute value of the slope is 2.

Video Solution

Step-by-Step Solution

To address this problem, we follow these steps:

  • Step 1: A linear function in slope-intercept form is y=mx+c y = mx + c . Given slope m=2|m| = 2, possible equations are y=2x+c y = 2x + c and y=2x+c y = -2x + c .
  • Step 2: Consider positivity for x>3 x > 3 condition.
    - For y=2x+c y = 2x + c : We need y=2x+c>0 y = 2x + c > 0 . Solving yields 2x>c 2x > -c , meaning the function is positive when x>c2 x > \frac{-c}{2} .
    - For y=2x+c y = -2x + c : Similarly, 2x+c>0-2x + c > 0 provides c>2x c > 2x or x<c2 x < \frac{c}{2} , implying negativity above x=c2 x = \frac{c}{2} .
  • Step 3: Examine behavior at x=3 x = 3 :
    - For y=2x+c y = 2x + c , it should be 2(3)+c>0 2(3) + c > 0 ; simplifying: 6+c>0c>6 6 + c > 0 \rightarrow c > -6 .
    - For y=2x+c y = -2x + c , since positive domain minimum is x>3 x > 3 , it’s negative x>c2 x > \frac{c}{2} .
  • Step 4: Confirms the correct function must work for any c>6 c > -6 , resultant choice: y=2x6 y = 2x - 6 . It remains positive as x increases past 3.

Thus, the correct equation satisfies all parameters: y=2x6 y = 2x - 6 .

Answer

y=2x6 y=2x-6