What is the first step in a proof by mathematical induction to show that "For all the positive integers n,1²+2²+dots+n²=n(n+1)(2n+1)/θ is true?
a. Prove that the formula is true for the (k+1) term.
b. Assume the formula is true for n=k.
c. Substitute k into the original formula.
d. Show that the formula is true when n=1.