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Teaching Mathematics: Foundations to Middle Years

Teaching Mathematics

Written by a group of highly respected and experienced teacher educators, the advice is based on current research and theories and, although written for pre-service teachers, there is much that will appeal to practising teachers.

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‘Proof’ that 2 = 1

let a = b

then a2 = ab

a2 - b2 = ab-b2

(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.