00:01
M and n are natural numbers with defining fee from integers to zm plus zn by fee of x, to the x mod m first coordinate and x mod n second coordinate.
00:16
So that fee is a group homomorphism and find the kernel.
00:22
So we want to look at fee of a plus b.
00:28
That's fee of a plus b mod m.
00:33
Sorry, not fee anymore.
00:36
We did the fee operation.
00:38
That's a plus b mod m and then a plus b mod n.
00:54
Now if i add two numbers and then do the modulus, that's the same as doing the modulus on each individually, adding and then doing the modulus.
01:03
So that's equal to a mod m plus b mod m and then doing the modulus.
01:18
And a mod n plus b mod n, b mod n.
01:32
Okay, so that's equal to a mod m, a mod m plus b mod m, because this plus plus operation is occurring inside of this group, right? and in this group, you add these two numbers, module, m.
02:10
And you add these two numbers, module, m.
02:14
But this here is just v of a, and this here is just v of b.
02:21
Okay.
02:22
So then we show that this is a homomorphism.
02:25
They're showing that i can do f f f of a plus b.
02:28
It's equal to f of a plus f of b.
02:30
Okay.
02:31
We want to find the kernel.
02:32
So the kernel of f is the set of a, and z such that fee of a is a zero element in here it will be zero zero.
02:53
Okay, so that's the set of a and z such that fee of a becomes a mod m, a mod m, that needs to be equal to zero, okay? so a mod m being zero means that m divides a, and a mod n being zero means n divides a.
03:19
So this is the set of a and z, such that m divides a and n divides a.
03:34
So this becomes, you know, all multiples of lcm, eminent.
03:51
So the kernel is all of the multiples of the least common multiple.
03:56
So really all common multiples of m &m.
04:03
Maybe that would be better.
04:04
All common multiples of m and m.
04:25
Okay, next.
04:26
M is going to be 12, m is 15, b is 410, c is, okay, let me just copy this down.
04:34
Good.
04:34
You want to work with.
04:43
Okay, m and b, c are defined, find a pre -image of fee, a b.
04:50
Okay, so i want to know for what values of x is v of x equal to b...