11^2 + 13^2 = 121 + 169 = 290
290 - 1 = 289 = 17^2
1 must be subtracted to give a perfect square.
The smallest number which when subtracted from the sum of squares of 11 and 13 gives a perfect square is
1. 1
2. 4
3. 5
4. 9
5. 8