For 2 non zero numbers x and y such that:
x = y
mutiply by x gives:
x² = xy
Subtract y² from both sides:
x² - y² = xy - y²
which can be written as:
(x+y)(x-y)=y(x-y)
Dividing by (x-y) gives:
x + y = y
Since x = y, we see that
2y = y
Divide by y gives:
2=1
Therefore:
1+1=1
x = y
mutiply by x gives:
x² = xy
Subtract y² from both sides:
x² - y² = xy - y²
which can be written as:
(x+y)(x-y)=y(x-y)
Dividing by (x-y) gives:
x + y = y
Since x = y, we see that
2y = y
Divide by y gives:
2=1
Therefore:
1+1=1