Find the mistake in the following “proof” that purports to

Chapter 5, Problem 19E

(choose chapter or problem)

Problem 19E

Find the mistake in the following “proof” that purports to show that every nonnegative integer power of every nonzero real number is 1.

“Proof: Let r be any nonzero real number and let the property P (n) be the equation rn = 1.

Show that P(0) is true: P (0) is true because r0 = 1 by definition of zeroth power.

Show that for all integers k≥ 0, if P(i) is true for all integers i from 0 through k, then P(k+ 1) is also true: Let k be any integer with k ≥0 and suppose that ri = 1 for all integers i from 0 through k. This is the inductive hypothesis. We must show that rk+1 = 1. Now

Thus rk+1 = 1 [as was to be shown].

[Since we have proved the basis step and the inductive step of the strong mathematical induction, we conclude that the given statement is true.]”