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Mathematics 7 Online
OpenStudy (anonymous):

Modular equation

OpenStudy (anonymous):

|dw:1415587285455:dw|

OpenStudy (anonymous):

how do you solve this?

OpenStudy (anonymous):

i give up i would probably start with \[m^7\equiv 26(33)\] and see if i could get a pattern of some kind

OpenStudy (anonymous):

you have a method you are supposed to use? btw the answer is 20

OpenStudy (anonymous):

must have something to do with \(33=3\times 7\) and primitive roots perhaps

OpenStudy (anonymous):

and perhaps the fact that \(\phi(33)=2\times 10=20\) so there are 20 congruence classes

OpenStudy (anonymous):

i dont understand T^T

OpenStudy (rsadhvika):

@FibonacciChick666

OpenStudy (fibonaccichick666):

I can do this!!!!!

OpenStudy (fibonaccichick666):

give me a minute I need my book

OpenStudy (rsadhvika):

\(\large m^7 \equiv 26 \pmod {3}\) \(\large m^7 \equiv 26 \pmod {11}\) same as \(\large m^7 \equiv 2 \pmod {3}\) \(\large m^7 \equiv 4 \pmod {11}\)

OpenStudy (fibonaccichick666):

I think that is legal

OpenStudy (rsadhvika):

i see "-1" satisfies first congruence

OpenStudy (rsadhvika):

should i check m= -5->5 for second congruence ?

OpenStudy (fibonaccichick666):

well, I was thinking we should expect multiple answers

OpenStudy (fibonaccichick666):

but hmm...

OpenStudy (fibonaccichick666):

ok yea, so we can use chinese remainder theorem

OpenStudy (fibonaccichick666):

\[m^7≡26(mod3)~~~~~~~~~ m^7≡26(mod11)\] \[m^7≡2(mod3)~~~~~~~~~~~~ m^7≡4(mod11)\]

OpenStudy (rsadhvika):

-1 satisfies mod 3 -2 satisfies mod 11 next we apply chinese remainder thm, thats it ? xD thought its more complicated for some reason haha!

OpenStudy (fibonaccichick666):

I think so.... That's all I'd do

OpenStudy (fibonaccichick666):

you might be able to use primitive roots though as suggested before, there is \(x^m-g\equiv 0 mod p\) where g is a prim root

OpenStudy (fibonaccichick666):

actually, 33 cannot have a primitive root.... soo

OpenStudy (rsadhvika):

chinese remainder thm wont work is it ?

OpenStudy (rsadhvika):

the solution to system : x^7 = 2 mod 3 x^7 = 4 mod 11 is not same as x = 2 mod 3 x = 9 mod 11 ?

OpenStudy (fibonaccichick666):

gotta ask, where did you get the 9?

OpenStudy (fibonaccichick666):

ah ok nvm

OpenStudy (rsadhvika):

just tried all the numbers from 0->10 for x^7 = 4 mod 11 only 9 satisfies

OpenStudy (fibonaccichick666):

ok I buy that

OpenStudy (fibonaccichick666):

I'd say try it

OpenStudy (fibonaccichick666):

why are you taking inverses again?

OpenStudy (rsadhvika):

one sec, let me review chinese remainder thm quick

OpenStudy (rsadhvika):

yeah there was a mistake, il delete

OpenStudy (fibonaccichick666):

although I guess you could just take the numbers from (2-32)^7 and see if they are congruent to 26?

OpenStudy (rsadhvika):

oh wolfram says it is 20, i must applying CRT incorrectly http://www.wolframalpha.com/input/?i=solve+x+%3D+2+mod+3%2C+x+%3D+9+mod+11

OpenStudy (fibonaccichick666):

then again http://www.di-mgt.com.au/rsa_alg.html

OpenStudy (fibonaccichick666):

guess you could use this for inspiration http://www.math.upenn.edu/~ssneha/soln2.pdf

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