Let n be a positive integer. We write x; for the ith digit of n. (I.e., if n = 217, then x1 = 7, x2 = 1 and x3 = 2.) In particular, n = x1 + x210+ + xk10k-1. Prove the following: (a) n = x1 + x2+ ...+ xk( mod 9). (b) n = x1 – x2 +...+ (-1)k-lxk( mod 11).

Elements Of Modern Algebra
8th Edition
ISBN:9781285463230
Author:Gilbert, Linda, Jimmie
Publisher:Gilbert, Linda, Jimmie
Chapter2: The Integers
Section2.5: Congruence Of Integers
Problem 29E: 29. Find the least positive integer that is congruent to the given sum, product, or power. a. ...
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Let n be a positive integer. We write x; for the ith digit of n. (I.e., if n = 217, then x1 = 7,
x2 = 1 and x3 = 2.) In particular, n = x1 + x210+
+ xk10k-1. Prove the following:
(a) n = x1 + x2+ ...+ xk( mod 9).
(b) n = x1 – x2 +...+ (-1)k-lxk( mod 11).
Transcribed Image Text:Let n be a positive integer. We write x; for the ith digit of n. (I.e., if n = 217, then x1 = 7, x2 = 1 and x3 = 2.) In particular, n = x1 + x210+ + xk10k-1. Prove the following: (a) n = x1 + x2+ ...+ xk( mod 9). (b) n = x1 – x2 +...+ (-1)k-lxk( mod 11).
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