Name: chuck kennedy
Who is asking: Teacher
Level: Secondary

1. Assume a=b
2. Multiply both sides by a, a²=ab
3. Subtract b², a²-b²=ab-b²
4. Factor (a-b)(a+b)=b(a-b)
5. Cancel like factors a+b=b
6. Substitue b for a b+b=b
7. Then 2b=b
8. Therefore 2=1

Please help!!A happy meal is riding on this one!!

The error is in step 5. Cancel like factors.

You can only cancel like nonzero factors. You cannot cancel 0 * 2 = 1 * 0 to get 2 = 1.

One way to understand this type of fallacy is to try the procedure with numbers. Suppose a = b = 5 and proceed through the steps.