JAMB - Mathematics (1999 - No. 28)
Evaluate \(\int^{1}_{-2}(x-1)^{2}dx\)
\(\frac{-10}{3}\)
7
9
11
Explanation
To evaluate the integral
\(\int_{-2}^{1} (x - 1)^{2} \, dx,\)
We first expand the integrand:
\((x - 1)^{2} = x^{2} - 2x + 1\)
Thus, the integral becomes:
\(\int_{-2}^{1} (x^{2} - 2x + 1) \, dx = \int_{-2}^{1} x^{2} \, dx - 2\int_{-2}^{1} x \, dx + \int_{-2}^{1} 1 \, dx\)
Now, we evaluate each integral:
For \(\int_{-2}^{1} x^{2} \, dx\):
\(\left[ \frac{x^{3}}{3} \right]_{-2}^{1} = \frac{1}{3} - \left(-\frac{8}{3}\right) = 3\)
For \(-2\int_{-2}^{1} x \, dx\):
\(-2\left[ \frac{x^{2}}{2} \right]_{-2}^{1} = -2\left(\frac{1}{2} - 2\right) = 3\)
For \(\int_{-2}^{1} 1 \, dx\):
\([x]_{-2}^{1} = 1 + 2 = 3\)
Combining the results: 3 + 3 + 3 = 9.
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