Câu hỏi:

\(I = - \int_a^5 | x - 5|dx + \int_5^b | x - 5|dx\)

\(\int_a^5 | x - 5|dx = \int_a^5 {(5 - x)} dx = \left. {\left( {5x - \frac{{{x^2}}}{2}} \right)} \right|_a^5 = \frac{{25}}{2} - \left( {5a - \frac{{{a^2}}}{2}} \right).\)

\(\int_5^b | x - 5|dx = \int_5^b {(x - 5)} dx = \left. {\left( {\frac{{{{\rm{x}}^2}}}{2} - 5{\rm{x}}} \right)} \right|_5^{\rm{b}} = \left( {\frac{{{{\rm{b}}^2}}}{2} - 5\;{\rm{b}}} \right) + \frac{{25}}{2}\)

\(I = \frac{{{a^2} + {b^2}}}{2} - 5a - 5b + 50\)