00:01
Hello, in the first sub -question given 9x is congruent to 21 mod 12 and 9x is congruent to 9 mod 12.
00:16
Let this be equation 1.
00:18
Gcd of 9 .12 is equal to 3 and 3 divides 9.
00:30
Thus solution of above congruence exists.
00:48
Therefore 9x is equal to 9 plus 12k.
00:54
Therefore 9x minus 12k is equal to 9.
00:58
We put y is equal to minus k.
01:03
Therefore we get 9x plus 12y is equal to 9.
01:08
Let us this be equation 2.
01:11
We know that 12 is equal to 9 into 1 plus 3 and 9 is equal to 3 into 3 plus 0.
01:21
Therefore 3 is equal to 12 minus 9 into 1 multiplying by 3 we get 9 is equal to 12 into 3 minus 9 into 3.
01:33
So, x is equal to minus 3, which is equal to 9, mod 12...