Math  /  Calculus

QuestionWe want to find the relative extrema of f(x)f(x). Here is the graph of its derivative f(x)f^{\prime}(x).
Use the graph of f(x)f^{\prime}(x) to identify locations of any relative maximum(s), relative minimum(s) and Horizontal Points of Inflection of f(x)f(x).

Studdy Solution

STEP 1

What is this asking? Where does our *original* function f(x)f(x) have maximums, minimums, and plateaus, given the graph of its *derivative* f(x)f'(x)? Watch out! Don't mix up f(x)f(x) and f(x)f'(x)!
We're looking for properties of f(x)f(x), but we're *given* f(x)f'(x).

STEP 2

1. Analyze the Derivative's Sign
2. Identify Relative Extrema
3. Identify Horizontal Points of Inflection

STEP 3

Let's **look** at where f(x)f'(x) is positive, negative, or zero. *Why*? Because the sign of the derivative tells us whether f(x)f(x) is increasing or decreasing!

STEP 4

f(x)f'(x) is positive before x=2x = -2.
This means f(x)f(x) is **increasing** up to that point.
Then, f(x)f'(x) becomes negative.
So f(x)f(x) switches to **decreasing** after x=2x = -2.

STEP 5

f(x)f'(x) is negative between x=2x = -2 and x=3x = 3.
This means f(x)f(x) is **decreasing** in this interval.

STEP 6

f(x)f'(x) is positive between x=3x = 3 and x=5x = 5.
This means f(x)f(x) is **increasing** in this interval.

STEP 7

f(x)f'(x) is negative after x=5x = 5.
This means f(x)f(x) is **decreasing** after this point.

STEP 8

A **relative maximum** occurs when f(x)f(x) *stops* increasing and *starts* decreasing.
This happens when f(x)f'(x) changes from positive to negative.

STEP 9

Looking back at our analysis, this happens at x=2x = \mathbf{-2}.
So, we have a relative maximum there!

STEP 10

A **relative minimum** occurs when f(x)f(x) *stops* decreasing and *starts* increasing.
This happens when f(x)f'(x) changes from negative to positive.

STEP 11

This happens at x=3x = \mathbf{3}!
So, we have a relative minimum there!

STEP 12

A **horizontal point of inflection** occurs when f(x)f'(x) is zero *and* the sign of f(x)f'(x) *doesn't* change.
This means f(x)f(x) momentarily flattens out but continues its current trend (increasing or decreasing).

STEP 13

At x=5x = \mathbf{5}, f(x)f'(x) is zero, but it goes from positive to negative.
This isn't a horizontal point of inflection, it's a relative maximum (which we already identified!).

STEP 14

f(x)f(x) has a **relative maximum** at x=2x = \mathbf{-2}, a **relative minimum** at x=3x = \mathbf{3}, and *no* horizontal points of inflection.

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