Question

Consider this function.

f(x) = |x – 4| + 6

If the domain is restricted to the portion of the graph with a positive slope, how are the domain and range of the function and its inverse related?

1.Since the domain of the original function is limited to x> 6, the range of the inverse function is y ≤ 6.
2.Since the domain of the original function is limited to x> 4, the range of the inverse function is y ≤ 1.
3.Since the range of the original function is limited to y> 6, the domain of the inverse function is x ≥ 6.
4.Since the range of the original function is limited to y> 4, the domain of the inverse function is x ≥ 1.

Answer 1

The domain of the original function with the positive slope is restricted to x > 4, and the range of f(x) is y ≥ 6. Therefore, the domain of the inverse function is x ≥ 6.

Step-by-step explanation:

The function given is f(x) = |x – 4| + 6. When restricting the domain to the portion of the graph with a positive slope, the function increases. In the absolute value function, the slope changes at the vertex, which here is when x = 4. For x > 4, the slope is +1 because the graph of the function is increasing. So, considering the domain x > 4 makes the graph of the function only represent the portion with a positive slope.

The range of the original function with the restricted domain is f(x) ≥ 6, because the lowest value of |x – 4| is 0 when x ≥ 4, which results in f(x) = 0 + 6 = 6 when x = 4. Consequently, the corresponding range of the inverse function must be the domain of the original function, and thus, the domain of the inverse function must be x ≥ 6.

Answer 2

3. Since the range of the original function is limited to y> 6, the domain of the inverse function is x ≥ 6.

Step-by-step explanation:

The domain of a function is the range of its inverse, and vice versa. The only answer choice that expresses this relationship is choice 3.

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Comment on the answer choice:

The slope of the function is undefined at x=4, so restricting the function domain to the portion with positive slope means the domain restriction of the function is x > 4. That also means the range restriction of the function is y > 6. The domain restriction of the inverse function is the same: x > 6, not x ≥ 6. The answer choice has an error.