They are: 25 minus 4 = 21
25 and 4 or 121 and 100
They are: 25-4 = 21
112 - 102 = 21
16
44
25
I think the question may refer to which two squares differ by 21. Two solutions : 112 - 102 = 121 - 100 = 21. 52 - 22 = 25 - 4 = 21.
The spacing between any two consecutive square numbers (n) and (n+1) is equal to (2n +1), so for 2n+1 =21, n =10 and the numbers are 121 and 100.However, there is a non-consecutive pair as well: 25 and 4.The squares lower than 100 are 1, 4, 9, 16, 25, 36, 49, 64, and 81, and an examination of these shows that there are no other pairs that satisfy the conditions.
-19
No
There are an infinite amount of answers to that, like: 25 - 0 30 - 5 21 - -4 118 - 93