Is 1,4,9,16 an arthmetic sequence

Determine whether the set of whole numbers is closed under addition. explain why the set is or is not closed. give an example.

Write numerical coefficient of y² in the expression 2x² - 15xy – 7y²

Aparticular telephone number is used to receive both voice calls and fax messages. suppose that 25% of the incoming calls involve fax messages, and consider a sample of 25 incoming calls. (a) what is the expected number of calls among the 25 that involve a fax message?