Mathematically show 1+1=1

I don't know whether this might help you in any way, but I'll post it anyway. Here goes.

Let a=b
2a-a=a

Substitue a with b:
2a-b=a

Since a=b,
2a-b = a
Add -b to both sides :
2a-b-b = a-b
2a-2b = a-b
2(a-b)=(a-b)
2 = (a-b)/(a-b)
2 = 1
1+1 = 1

Thus, 1+1=1 is mathematically shown.