Question 1
A function f(x) passes through the points (−3,7) and (5,−1). If g(x)=f(x−2)+3, what is the average rate of change of g(x) over the interval [−1,7]?
- −1 (correct answer)
- −21
- 21
- 1
Explanation: First, find the average rate of change of f(x) over [−3,5]: 5−(−3)f(5)−f(−3)=8−1−7=−1. For g(x)=f(x−2)+3, we need g(−1) and g(7). Since g(−1)=f(−3)+3=7+3=10 and g(7)=f(5)+3=−1+3=2, the average rate of change is 7−(−1)2−10=8−8=−1. Choice B results from incorrectly using the original interval length of 8 in the denominator twice. Choice C is the negative of the correct answer. Choice D ignores the negative sign from the calculation.
Question 2
The function k(x) has an average rate of change of −3 over the interval [2,6] and an average rate of change of 5 over the interval [6,10]. If k(2)=8, what is k(8) assuming k(x) is linear on each interval?
- −2
- 2
- 6 (correct answer)
- 10
Explanation: Since k(x) has average rate of change −3 over [2,6] and k(2)=8, we have 6−2k(6)−k(2)=−3, so 4k(6)−8=−3, giving k(6)−8=−12, thus k(6)=−4. Since k(x) is linear on [6,10] with rate 5, we have k(8)=k(6)+5⋅(8−6)=−4+5⋅2=−4+10=6. Choice A would result from calculation errors. Choice B incorrectly uses the rate from the first interval. Choice D is k(6)+14, a common arithmetic error.