d 2 y d t 2 + w 2 y = 0 {\displaystyle {\frac {d^{2}y}{dt^{2}}}+w^{2}y=0}
T = 2 π l g {\displaystyle T=2\pi {\sqrt {\frac {l}{g}}}}
d 2 y d t 2 + 2 b d y d t + w 2 y = P sin w t {\displaystyle {\frac {d^{2}y}{dt^{2}}}+2b{\frac {dy}{dt}}+w^{2}y=P\sin {wt}}
i2
H2SO4
NH3
