Question

Can someone explain this integral rule to me?

Answer 1

integrating \[e ^{-3t}.dt\] ?

Answer 2

Power rule or u-sub should be fine
\[\int\limits e^{-3t}dt \\ \\ u=-3t \\ \\ du=-3dt \\ \\-\frac{1}{3} \int\limits e^udu\]
integral of e^u is e^u+c

Answer 3

e^ax = 1/ae^ax?