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## 'Always Two' printed from http://nrich.maths.org/

As some solutions are easily spotted, you may be able to find
solutions by trial and error. You still need to prove that the
solutions you have found are the only ones.

Write down three simultaneous equations from the statement of the
problem.

Take care to keep the symmetry of the expressions.

In pairs subtract one equation from another.

What can you deduce if the product of two linear factors is
zero?