1. State the coordinates of $A$, $B$, and $C$ found in part (a)
From part (a), we have A=(32,0), B=(9,5), and C=(10.5,0).
2. Set up the integral for the area under the curve from $A$ to the $x$-coordinate of $B$
Area under curve =∫329(3x−2)21dx
3. Evaluate the integral
∫329(3x−2)21dx=[23×3(3x−2)23]329=[92(3x−2)23]329
=92(25)23−92(0)23=92(125)=9250
4. Calculate the area of the triangle formed by the normal and the $x$-axis
The region under the normal from x=9 to x=10.5 is a triangle with base 10.5−9=1.5 and height 5.
Area of triangle =21×1.5×5=415
5. Find the total area of the shaded region
Total area =9250+415=361000+135=361135=313619
答案361135 or 313619