Square of 19
i) Subtract 1 from the number ; 19-1 =18
ii) left the right hand side 9 from the given number; so from 19; 1 will become balance.
(iii) in the result of (ii) add 1 i.e. 1+1 =2
(iv) multiply the result of (i) with result from (iii) i.e. 18*2 =36
(v) write 1 on R.H.side of the answer of (iv) i.e. write 1 with 36 it will 361

So (19)2 = 361

similarly for (49)2=

i) 49-1 =48
ii) 4+1 =5
iii) 48*5 = 240
iv) write 1 on Right Hand side of the result of (iii)
So answer = 2401.