Solution
To find the area A, we need to integrate the function y=x∣x−3∣ from x=−1 to x=2.
Step 1: Define the function without absolute value
The term ∣x−3∣ changes its behavior based on whether x is greater than or less than 3.
Since our interval of integration is [−1,2], x is always less than 3. Therefore, in this range:
Step 2: Set up the integral for Area A
The area A is given by:
Let's check if the curve crosses the x-axis between −1 and 2.
3x−x2=0⟹x(3−x)=0. The roots are x=0 and x=3.
Since x=0 lies within our interval [−1,2], the function changes sign at 0.
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For x∈[−1,0]: y is negative.
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For x∈[0,2]: y is positive.
So, the total area A is:
A=∫−10−(3x−x2)dx+∫02(3x−x2)dx
A=∫−10(x2−3x)dx+∫02(3x−x2)dx
Step 3: Evaluate the integrals
Applying the power rule ∫xndx=n+1xn+1:
First part:
[3x3−23x2]−10=(0−0)−(3(−1)3−23(−1)2)
=−(−31−23)=−(−62+9)=611
Second part:
[23x2−3x3]02=(23(2)2−3(2)3)−(0)
=(212−38)=6−38=318−8=310
Total Area A:
A=611+310=611+620=631
Step 4: Find 12A