Answers:
Describing the Error:
Choice B) The function is nonlinear and the increase in y is not constant.
Correcting the Error:
As x increases by a constant amount, y needs to increase or decrease by the same amount for the function to be linear.
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Explanation:
Each time x goes up by 2, y is being multiplied by 4.
It may appear y is increasing at a constant rate, but this is not true. The jump from y = 4 to y = 16 is +12; while the jump from y = 16 to y = 64 is +48. The increase in y is not the same each time. This is just a rephrasing of what is discussed in the "correcting the error" section above.
So this is why the function is nonlinear. It turns out that this function is an exponential. Specifically, this is the function y = 2^x. For instance, if x = 8, then y = 2^x = 2^8 = 256. Graphing this function produces a curve that isn't a straight line, which is visual confirmation the function is nonlinear.
