Q4. Exponential Growth

Explanation

For a question like this you have to plug in options and test it out. But you should be able to very quickly eliminate (A) and (B).

You'll notice in the table that for every incremental (+1) increase in X, the value of Y increases by the same amount. This means that the formula must be linear.

(A) and (B) are both exponential formulas. So that leaves (C) and (D). An important rule for plug-in/test questions: Make sure you test AT LEAST 2 options. If you had tested only x = 1, both (C) and (D) would work. But when you test x = 2, you realize that (C) doesn't work and that only (D) works.

Lesson

Linear growth = additive effect on the independent variable (y).

Exponential growth = multiplicative effect on the independent variable.

Source: College Board SAT Test 6

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