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Discrete Math 8 Online
OpenStudy (bee_see):

I'm having trouble with modular arithmetic. There are the problems:

OpenStudy (bee_see):

OpenStudy (misty1212):

HI!!

OpenStudy (bee_see):

Hello.

OpenStudy (misty1212):

work directly from the definition that is what you have to do

OpenStudy (bee_see):

is a ≡ b (mod m) the same as m|(a − b).?

OpenStudy (bee_see):

are these equal to each other?

OpenStudy (misty1212):

\[a\equiv a(\text{mod } m )\] means \(m|a-a\)

OpenStudy (misty1212):

yes that is what it means just notation is all

OpenStudy (misty1212):

pretty clear that \(m\) divides \(a-a\) because any number divides zero

OpenStudy (misty1212):

now that you know what to do, i am sure you can do the rest

OpenStudy (bee_see):

I thought it was m divides (a-b)

jimthompson5910 (jim_thompson5910):

Recall that \[\Large a | b \ \Leftrightarrow \ a*k = b\] i.e. `a | b`, or 'a' divides b, is the same as saying 'a' is a factor of b

jimthompson5910 (jim_thompson5910):

where k is some integer

OpenStudy (misty1212):

yes in general it is but your first job is to show that \[a\equiv a(\text{mod }m)\]

OpenStudy (bee_see):

what exactly is a ≡ b (mod m)? what does that mean?

OpenStudy (misty1212):

so where you see a \(b\) put an \(a\) and you get \[m|a-a\]

OpenStudy (misty1212):

do you know what \(m|a-b\) means ?

OpenStudy (bee_see):

mk= a-b?

OpenStudy (misty1212):

for example \[2\equiv 12(\text{mod}5)\] because \[5|12-2\]

OpenStudy (misty1212):

that means five goes in to \(12-2\) evenly

OpenStudy (misty1212):

or you can put what you wrote, same thing, but for your proof you can use the definition

OpenStudy (bee_see):

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