June 2018 p11 q10
1277
The curve with equation \(y = x^3 - 2x^2 + 5x\) passes through the origin.
Showing all necessary working, find the area of the region enclosed by the curve, the \(x\)-axis and the line \(x = 6\).
Solution
To find the area under the curve \(y = x^3 - 2x^2 + 5x\) from \(x = 0\) to \(x = 6\), we need to integrate the function with respect to \(x\).
The integral of \(y = x^3 - 2x^2 + 5x\) is:
\(\int (x^3 - 2x^2 + 5x) \, dx = \frac{x^4}{4} - \frac{2x^3}{3} + \frac{5x^2}{2} + C\)
We evaluate this definite integral from \(x = 0\) to \(x = 6\):
\(\left[ \frac{x^4}{4} - \frac{2x^3}{3} + \frac{5x^2}{2} \right]_0^6\)
Substitute \(x = 6\):
\(\frac{6^4}{4} - \frac{2 \times 6^3}{3} + \frac{5 \times 6^2}{2} = \frac{1296}{4} - \frac{2 \times 216}{3} + \frac{5 \times 36}{2}\)
\(= 324 - 144 + 90\)
\(= 270\)
Thus, the area of the region is 270.
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