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.
Let P(n):c(a1+a2+…+an) = ca1+ca2+…+can ,for all natural
numbers, n ≥ 2.
Step1: For n=2,
P(2)
LHS= c(a1 + a2)
RHS= c a1 + ca2
As, it is given that c(a1 + a2) = c a1 + ca2
Thus, P(2) is true.
Step2: For n=k,
Let P(k) be true
So, c(a1+a2+…+ak) = ca1+ca2+…+cak
Now, we need to show P(k+1) is true whenever P(k) is true.
P(k+1):
LHS= c(a1+a2+…+aK+ak+1)
=c[(a1+a2+…+aK)+ak+1]
=c(a1+a2+…+aK)+cak+1
=ca1+ca2+…+caK+cak+1
=RHS
Thus, P(k+1) is true, so by mathematical induction P(n) is true.