2

Part of 2008 Bosnia and Herzegovina Junior BMO TST

Problems(1)

easy divisibility including 7

Source: BiH JBMO TST 08 problem 2

x,y,z

be positive integers. If

7

divides (x\plus{}6y)(2x\plus{}5y)(3x\plus{}4y) than prove that

343

also divides it.

modular arithmeticnumber theory proposednumber theory