Question

x+5=8 find x

Answer 1

there must be several pre-algebras with the same picture

Answer 2

here's one simple way to find the answer: 8-5=3, x=3

Answer 3

aecampbell, how did you find that 8?

Answer 4

took it from the equation. "x+5=8"

Answer 5

Could you help me with another problem? The teacher said that we have to use that answer to determine the inverse of 7 modulo 17 using Euler's theorem. Recall that if \(\gcd(a,n)=1\), then\[a^{\phi(n)}\equiv1(\text{mod }n).\]

Answer 6

Naturally, \(\phi\) is Euler's totient.

Answer 7

I am sorry, that is far too complex for my understanding. I may have to learn this with you!

Answer 8

Well, I know that \(\phi(17)=16\). Thus\[7^{16}\equiv1(\text{mod }17),\]since \(\gcd(7,17)=1\). I think I can manipulate the LHS of that congruence like this:\[7^{16}\equiv7\cdot7^{15}\equiv1(\text{mod }17).\] It follows that the inverse should be just \(7^{15}(\text{mod }17)\), which (according to my calculator) yields \(5\). Therefore, \(17{-1}\equiv5(\text{mod }17)\). What do you think?

Answer 9

I meant to say \(7^{-1}\equiv5(\text{mod }17)\) in that last expression.

Answer 10

x = 3

Answer 11

don't be lazy. if you want the inverse of 7 mod 17 you only have sixteen numbers to check.

Answer 12

17 = 2*7 + 3
7 = 2*3+1

1= 7-2*3
1= 7 - 2(17-2*7)
1=5 * 7-2*17
your inverse is 5
just checking this method

Answer 13

We call that the reverse division algorithm. :)

Answer 14

ok here is a nice question
i am trying to recall a formula for a bijection from N to Q and i cannot seem to remember it.

Answer 15

http://openstudy.com/study?login#/updates/4f62a03fe4b079c5c6317a95