Solution for Section 3.9 Question 2

2. First apply the Euclidean Algorithm to 105 and 56 to find gcd(105, 56).

105

=

56 · 1 + 49     (equation 1)
56 = 49 · 1 + 7 (equation 2)
49 = 7 · 7 + 0 (equation 3)

Thus, gcd(105, 56) = 7. Since 7 | -14, we know that a solution exists to the linear Diophantine equation 105m + 56n = -14.

Now work backwards through the equations of the Euclidean Algorithm to find a solution.

From equation 2 we see that:

7 = 56 - 49 · 1
= 56 - [105 - 56 · 1] · 1
= 56 · 2 - 105 · 1

Therefore,     105(-1) + 56(2) = 7.          So, we multiply both sides of the equation by -2 to get:      105(2) + 56(-4) = -14.

Hence m = 2 and n = -4 is one solution to the linear Diophantine equation 105m + 56n = -14.

Back to Section 3.9