Whole numbers less than 20 are 19, 18, 17, 16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, 1. How to know if they are divisible by 3? Add the numbers, and if the sum is divisible by 3.
√z = 13 - 8 √z = 5 z = 5² z = 25 In this case the z can be any number, however z cannot be less than 0 and that is the restriction. (for example; √-1 = irrational number, cannot be solved.)
