# Chain rule question (differential termination)

Why is the following equation true? given: $$x '= x + vt$$,
$$frac { partial} { partial x } = frac { partial x} { partial x } frac { partial} { partial x} + frac { partial t } { partial x } frac { partial} { partial t}$$,
If that were not 1 = 2, if you can pick up the differentials (z. $$frac { partial x} { partial x} = 1$$)