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## 'Proof Sorter - Quadratic Equation' printed from http://nrich.maths.org/

Why do this problem?
This is one of a series of jumbled proofs. We think that sorting
the steps of the proof and the reasons, into the right order will
help people to understand and remember the derivation of the
formula for the roots of a quadratic equation.

Possible approach

We
hope this activity will be particularly useful in pair or group
work, where interpretation of the text can be shared and the
justification of choices can be tested on fellow
students.

Key questions

Which
blue statement looks like a starter?

Which
line of algebra looks like it belongs with that
statement?

Now
look at the actions on offer : Subtract, Divide, Take and Complete.
Can you find a line of algebra to go with each of those?

Is
there a sequence you can find by following the algebra?