SOLUTION: Is this closed under addition? {7,14,21,28,...} Margarita

Algebra ->  Real-numbers -> SOLUTION: Is this closed under addition? {7,14,21,28,...} Margarita      Log On


   

Question 380925: Is this closed under addition?
{7,14,21,28,...}

Margarita
Answer by jim_thompson5910(35256) About Me  (Show Source):
You can put this solution on YOUR website!
Yes because every number is in the form 7n where n is a positive integer


So take two numbers say 7n and 7m and add them to get 7n+7m=7(n+m) which is a multiple of 7, which means that this set is closed under addition.