Finding Absolute Extrema — Question 1

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Question 1

Let: f(x)=x3−6x2+9x+2f(x) = x^3 - 6x^2 + 9x + 2

Find the absolute maximum and minimum values of f(x)f(x) on the closed interval [0,4][0, 4].

Original worksheet page 1: question and worked solution for 4-4-001
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Question 1 - Solution

We are given: f(x)=x3−6x2+9x+2f(x) = x^3 - 6x^2 + 9x + 2

Step 1: Find critical points

f′(x)=3x2−12x+9=3(x−1)(x−3)=0⇒x=1,3f'(x) = 3x^2 - 12x + 9 = 3(x - 1)(x - 3) = 0 \Rightarrow x = 1, \ 3

Step 2: Evaluate at endpoints and critical points in [0,4][0, 4]

f(0)=2f(1)=6f(3)=2f(4)=6\begin{aligned} f(0) &= 2 \\ f(1) &= 6 \\ f(3) &= 2 \\ f(4) &= 6 \end{aligned}

Absolute Maximum: 6\boxed{6} at x=1x = 1 and x=4x = 4

Absolute Minimum: 2\boxed{2} at x=0x = 0 and x=3x = 3

Graph of the function on [0,4][0,4]

See the diagram in the original worksheet below.

Original worksheet page 2: question and worked solution for 4-4-001

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