Which of the following numbers are perfect cubes? 1728, 106480

4 Write cubes of 5 natural numbers which are of the form 3n+1 (e.g 4, 7, 10, ...) and verify the following: 'The cube of a natural number of the form 3n +1 is a natural number of the same form'. 5 Write cubes of 5 natural numbers which are of the form 3n + 2 (e.g. 5, 8, 11, …) and verify the following: 'The cube of a natural number of the form 3n + 2 is a natural number of the same form'. 7 What is the smallest number by which 392 must be multiplied so that the product is a perfect cube ? 8 What is the smallest number by which 8640 must be divided so that the quotient is a perfect cube ?