Back to Calculate average rate of change — Problem 4 · Task Set 11

HSF.IF.B.6 Tutor Intake — Average Rate of Change

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Grade 9·11 problems·~14 min·Common Core Math - HS Functions·group·hsf-if-b-6

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Procedures

A student wants to find the average rate of change of $g(x) = 2x + 5$
from $x = 1$ to $x = 4$ . They compute:

$\frac{g(1) - g(4)}{4 - 1} = \frac{7 - 13}{3} = \frac{-6}{3} = -2$

The correct answer is $+2$ . What error did the student make?

They used the wrong formula for $g$ .

They subtracted the numerator in the wrong order (used $g(a) - g(b)$ instead of $g(b) - g(a)$ ).

They divided by 3 instead of 2.

They should have added the function values instead of subtracting.