To identify linear growth between a quantity and the variable x, what property should the quantity’s values have at equal intervals of x?

Correct answer: The differences between consecutive values of the quantity must be constant

In linear growth, equal increases in x produce the same change in y each time. For example, when x rises by 1, y-differences may be 5, 5, 5. A constant ratio indicates exponential growth. Exam tip: check first differences first.