Choose the functions that fit the following description:
The function is positive in the domain 2 < x .
a. y=3x+4
b. y=2x−4
c. y=−2x+4
d. y=2
e. y=4x−8
f. y=5x−14
To determine which functions are positive for the domain x>2, we evaluate each function at x=2 and use their properties:
- Function y=3x+4: At x=2, y=3(2)+4=10, which is positive. As this is a linear function with a positive slope, it remains positive for x>2.
- Function y=2x−4: At x=2, y=2(2)−4=0. The function becomes positive for x>2, as the slope is positive.
- Function y=−2x+4: At x=2, y=−2(2)+4=0. The slope is negative, making it negative for x>2.
- Function y=2: This is a constant function with value 2, which is positive regardless of x.
- Function y=4x−8: At x=2, y=4(2)−8=0. The positive slope indicates that it becomes positive for x>2.
- Function y=5x−14: At x=2, y=5(2)−14=−4, which is negative, although it becomes positive for x>2 (since the slope is positive, it crosses the x-axis soon after x=2).
Based on this analysis, the correct answer is that the functions a, b, d, and e are positive for x>2.