Home > Student activities > National Maths Day > National Maths Day 2014 > ‘Proof’ that 2 = 1

# ‘Proof’ that 2 = 1

**let a = b**

**then a ^{2} = ab**

**a ^{2} - b^{2} = ab-b^{2}**

**(a-b)(a+b) = b(a-b)**

**a+b = b**

**substituting b+b = b**

**2b = b**

**2 = 1**

**Where is the error made?**

You need to be aware that a – b = 0. This false proof relies on dividing both sides of an equation by zero which should not be done.