Explanation:
Hey there!
Let's take out the square of 1st ten natural numbers to find out the exact answer.
1² = 1
2² = 4
3² = 9
4² = 16
5² = 25
6² = 36
7² = 49
8² = 64
9² = 81
10² = 100
Now; You can take any of these numbers and subtract from their squares.
So, let's check 6² and 5²
36-25 = 11 which is not equal to 19
Again check for 10²-9²
100 - 81 = 19 (True value)
Therefore, 19 can be expressed as the difference of square of 10 and 9.
Hope it helps!