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**Jaswahhihi****Member**- Registered: 2005-07-23
- Posts: 11

Hi.

Having real problems understading my lecutre notes about this.

Can anyone do this question and explain how you get the answer please?

Thanks

Determine whether or not there is a solution; if there is, find the General Solution.

18x = 21 mod 25

EDIT -(Oh and if that doesnt have a solution heres another:

6x = 5 mod 13)

*Last edited by Jaswahhihi (2006-10-19 05:52:35)*

98% of the teenage population does or has tried smoking pot. If you're one of the 2% who hasn't, copy & paste this into your signature.

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**Ricky****Moderator**- Registered: 2005-12-04
- Posts: 3,791

18x = 21 mod 25

You know that 18 = -7 mod 25 and 21 = -4 mod 25, so the problem becomes:

-7x = -4 mod 25

Which means:

25 | -7x + 4

Now find an x which statisfies this.

98% of the teenage population does or has tried smoking pot. If you're one of the 2% who hasn't, copy & paste this into your signature.

98% of the teenage population believes the myth that 98% of the teenage population has smoked pot. If you're one of the 2% who doesn't believe this, copy & paste this into your signature.

"In the real world, this would be a problem. But in mathematics, we can just define a place where this problem doesn't exist. So we'll go ahead and do that now..."

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**Jaswahhihi****Member**- Registered: 2005-07-23
- Posts: 11

ah no mate, Im just after getting the origonal expression: ax=b mod m

into the form:

x = c mod m'

where apparently m' = m/hcf(a,m)

Lol, I havent logged onto this forum in a few years, I didnt reaslise I still had that siggy

98% of the teenage population does or has tried smoking pot. If you're one of the 2% who hasn't, copy & paste this into your signature.

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**mathsyperson****Moderator**- Registered: 2005-06-22
- Posts: 4,900

98% of the teenage population doesn't collect pots.

Why did the vector cross the road?

It wanted to be normal.

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**luca-deltodesco****Member**- Registered: 2006-05-05
- Posts: 1,470

Ricky wrote:

98% of the teenage population believes the myth that 98% of the teenage population has smoked pot. If you're one of the 2% who doesn't believe this, copy & paste this into your signature.

actually, roughly 80% of teens i know, do or have indeed tried pot.

The Beginning Of All Things To End.

The End Of All Things To Come.

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**Ricky****Moderator**- Registered: 2005-12-04
- Posts: 3,791

First off, how do you judge 80%? Did you count? And how do you know they are telling the truth?

Most studies, it's around 40-45%.

Jaswahhihi, I'm confused at what you actually want. I thought you wanted to solve for x. Is this incorrect?

"In the real world, this would be a problem. But in mathematics, we can just define a place where this problem doesn't exist. So we'll go ahead and do that now..."

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**Jaswahhihi****Member**- Registered: 2005-07-23
- Posts: 11

Yeh I needed a general solution.

But Its ok now, went to a help lecture and got the info I needed.

Thanks for the input though

(on my sig aswell )

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