Proof that 2=1

The following are my steps when I proved that $2=1$ .

Step 1. Suppose that $:$ $y=b$

Step 2. Multiply both sides by $y$ $:$ $y^2=yb$

Step 3. Subtract $b^2$ from both sides $:$ $y^2-b^2=yb-b^2$

Step 4. Factor both sides $:$ $(y-b)(y+b)=b(y-b)$

Step 5. Divide both sides by $y-b$ $:$ $y+b=b$

Step 6. Since $y=b$ , substitute $:$ $b+b=b$ or $2b=b$

Step 7. Divide both sides by $b$ $:$ $2=1$

Is there something with my calculation? If your answer is $no$ , give your answer as $10$ . If your answer is $yes$ , input the step number which I first committed a mistake.