SAT Linear Functions study notes

In f(x) = mx + b, b is the starting value and m tells you how much the output changes when x rises by one. On a graph, slope is rise divided by run. In a word problem, its units usually tell you whether you found the right quantity.

Worked example

A tank begins with 18 liters and fills at 4 liters per minute. What does f(t) = 18 + 4t predict after 7 minutes?

Substitute t = 7: f(7) = 18 + 28 = 46 liters. The 18 is the initial amount; 4 is the rate per minute.

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