The integrand after substitution (after constants taken out) should be \(\displaystyle 1\). Right,
\(\displaystyle \int_{1}^{5} 3^{2x} dx\)
\(\displaystyle u = 3^{2x}\)
\(\displaystyle du = 3^{2x} * \ln 3 * 2 dx\)
\(\displaystyle \dfrac{du}{ \ln 3 * 2} = 3^{2x} dx\)
\(\displaystyle \displaystyle \dfrac{1}{2 \ln 3} \int_{9}^{59049} du\)
....YES
\(\displaystyle \int_{9}^{59049} \dfrac{du}{2 \ln 3}\)
..........Unnecessary - just leave the constant outside
\(\displaystyle \dfrac{1}{2\ln 3} |_{9}^{59049} \)
................\(\displaystyle \int du = u\),
...Where is the "u" ?