Question

Geraldine is asked to explain the limits on the range of an exponential equation using the function f(x) = 2x. She makes these two statements:

1. As x increases infinitely, the y-values are continually doubled for each single increase in x.
2. As x decreases infinitely, the y-values are continually halved for each single decrease in x.

She concludes that there are no limits within the set of real numbers on the range of this exponential function. Which best explains the accuracy of Geraldine’s statements and her conclusion in the four options below?

Statement 1 is incorrect because the y-values are increased by 2, not doubled.
Statement 2 is incorrect because the y-values are doubled, not halved.
The conclusion is incorrect because the range is limited to the set of integers.
The conclusion is incorrect because the range is limited to the set of positive real numbers.

Answer 1

Option 4 is best.

Explanation: Interpreting f(x) = 2^x (the intended exponential), Statements 1 and 2 are correct: increasing x by 1 multiplies y by 2 (doubling), decreasing x by 1 divides y by 2 (halving). The conclusion is wrong because the range is not all real numbers — it is limited to the positive real numbers: range = (0, ∞).

(If the function were actually f(x) = 2x (linear), then the doubling/halving statements would be wrong and the range would be all real numbers.)