\(\displaystyle L = \int_a^b f(x) \: dx\)

\(\displaystyle L = \int_c^d f(y) \: dy\)

\(\displaystyle L = \int_a^b f(x) - g(x) \: dx\)

\(\displaystyle L = \int_c^d f(y) - g(y) \: dy\)