In which step is the error?

Question

Step 1: Let x = 1 and y = 1.
Step 2: By substitution xy = y^2.
Step 3: Multiplying both sides by -1, -xy= -y^2.
Step 4: Adding x^2 to both sides, x^2-xy=x^2-y^2.
Step 5: Factoring, x(x-y)=(x+y)(x-y).
Step 6: Dividing both sides by x-y, x=x+y.
Step 7. By substitution, 1=1+1
Step 8: 1 = 2.

Answer 1

step 6

x = y = 1

so division by x-y is division by zero
a BIG no-no