Step-by-step explanation:
(b) If
then
Note that
cancel out so we get

Solving for
we get

(c) I'm not sure what the problem is asking for but here goes. As r doubles,
becomes

Kilogram is an SI unit for mass.
Ounce and pound refer to American system for measuring things, and decakilogram is not the "basic" unit, but kilogram is.
Step-by-step explanation:
try doing a2+b2=c2 it will help
8) terminating
9) repeating