1. A positive integer is divisible by 9 if and only if the sum of its digits is divisible by 9. if n is a positive integer, for which of the following values of k is 25*10ⁿ+k*10²ⁿdivisible by 9?
2. if n is a positive integer and n² is divisible by 72, then the largest positive integer that must divide n is?