The distributive law from algebra states that for real numbers
c, a1 and a2, we have c(a1 + a2) = c a1 + ca2
Use this law and mathematical induction to prove that, for all
natural numbers, n ≥ 2, if c, a1, a2, …... an are any real numbers,
then c(a1 + a2 +…+ an) = c a1 + c a2 +…+ c an.