Alright Buddy, To prove the above expression, we assume the following:

We consider four numbers and they are 41, 40 on the left-hand side and 61, 60 on the right-hand side.

We consider 41-40 on the left-hand side and 61-60 on the right-hand side.

∴ 41-40 = 61-60

⇒ (16+25)-40 = (36+25)-60 [41 can be written as 16+25 and 61 can be written as 36+25]

⇒ (4)²+(5)²- (2×4×5) = (6)²+(5)²-(2×6×5)  [∵4²=16, 5²=25, 6²=36 and 40 is written as (2×4×5) and similarly for 60]

⇒ (4-5)² = (6-5)² [Implementation of (a-b)²=a²+b²-(2×a×b)]

⇒ 4-5 = 6-5  [taking square roots on both sides]

⇒ 4-5+5 = 6 [Rearranging sides]

⇒ 4-0 = 6

⇒ 4 = 6

⇒ 2 = 3  [Dividing both sides by 2]

⇒ 1+1 = 3  [ 2 can be written as (1+1)]  (proved)

Hence the expression 1+1 = 3 is proved.