Algebra practice question

Answer: B. 5

First find the rate of change: as x rises from 2 to 5, f rises from 13 to 25, so the slope is (25 - 13) / (5 - 2) = 12 / 3 = 4. To reach x = 0 from x = 2, x falls by 2, so f falls by 2(4) = 8: f(0) = 13 - 8 = 5.

Why the other answers are wrong

A. 4

4 is the slope, the amount f changes per unit of x — not the value of f at x = 0. Use the slope to step back from a known point.

C. 9

You stepped back only one unit, from x = 2 to x = 1, giving 13 - 4 = 9. x = 0 is two units back, so subtract 8.

D. 21

You stepped in the wrong direction: 13 + 8 = 21. Going from x = 2 down to x = 0 means f decreases, not increases.

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