Discrete Mathematics and Its Applications, Seventh Edition

Published by McGraw-Hill Education
ISBN 10: 0073383090
ISBN 13: 978-0-07338-309-5

Chapter 4 - Section 4.4 - Solving Congruences - Exercises - Page 284: 5

Answer

Following the procedure of Example 2, we carry out the Euclidean algorithm to find gcd( 4, 9): 9=2·4+1 4 = 4 · 1 Then we work backwards to rewrite the gcd (the last nonzero remainder, which is 1 here) in terms of 4 and 9: 1=9-2·4 Therefore the Bezout coefficients of 9 and 4 are 1 and -2, respectively. The coefficient of 4 is our desired answer, namely -2, which is the same as 7 modulo 9. Note that this agrees with our answer in Exercise 3.

Work Step by Step

Following the procedure of Example 2, we carry out the Euclidean algorithm to find gcd( 4, 9): 9=2·4+1 4 = 4 · 1 Then we work backwards to rewrite the gcd (the last nonzero remainder, which is 1 here) in terms of 4 and 9: 1=9-2·4 Therefore the Bezout coefficients of 9 and 4 are 1 and -2, respectively. The coefficient of 4 is our desired answer, namely -2, which is the same as 7 modulo 9. Note that this agrees with our answer in Exercise 3.
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