Cho \(\int\limits_2^5 {\frac{{dx}}{x}} = \ln a\). Tìm a.

Cho \(\int\limits_2^5 {\frac{{dx}}{x}} = \ln a\). Tìm a.
A. \(a = \frac{5}{2}\)
B. \(a = 2\)
C. \(a =5\)
D. \(a = \frac{2}{5}\)

Ta có: \(\int\limits_2^5 {\frac{{dx}}{x}} = \ln a \Leftrightarrow \left. {\ln \left| x \right|} \right|_2^5 = \ln a \Leftrightarrow \ln 5 - \ln 2 = \ln a \Leftrightarrow \ln \frac{5}{2} = \ln a \Leftrightarrow a = \frac{5}{2}\)