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**1. aRb on Z if 5|2a+3b**

**2. Since 5|2a+3b, 2a+3b=5m, so 2a=5m-3b.**

**3. Consider 3a+2b=2a+2b+a=5m-3b+2b+a=5m-b+a. I can't show that 5 divides that, but there is another way to wrangle that into a better form. I need help seeing how that works. Thanks.**

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