大家帮我看看这个题怎么解，郁闷阿！

Consider the Fan laws
a) Show that if the laws for diameter change with fixed tip speed are correct, then the laws for diameter change with fixed rotational speed follow.
b) Show that if the laws for density change at fixed rotational speed and flow rate are correct, then the laws for density change at fixed head and for density change at fixed mass flow also follow.