method to find a least positive number that should be added to 1515 to become a perfect square
1. Get a calculator.
2. Find the square root of 1515.
3. You will get 38.92300091
4. Take the next higher whole number to that, which is 39
5. Square 39. That is, multiply 39x39
6. You will get 1521, which is a perfect square, since it is 39²
7. Subtract 1521 - 1515
8. You will get 6.
9. The answer is 6, because 6 is how much you will have to add to
1515 to get the first perfect square which is greater than 1515,
which is 1521.
Edwin