- #1
gummz
- 32
- 2
Homework Statement
Let S = { (x,y) in Z | 5x+7y is divisible by 3 }
Show that S is symmetrical.
Homework Equations
None apart from basic algebraic knowledge.
The Attempt at a Solution
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The only thing I can think of is starting with 3a = 5x+7y and putting x (or y) into the corresponding number 5y+7x and show that that turns out to be a multiple of 3, to show that it is symmetrical. But that leads me nowhere as far as I can tell:
5y+7x = 5y + 7 * (3a-7y) / 5