Stage: 3 Challenge Level: 
Add up all 5 equations given below. What do you notice?
Solve the system and find the values of a , b , c , d and e .
b + c + d + e = 4
a + c + d + e = 5
a + b + d + e = 1
a + b + c + e = 2
a + b + c + d = 0
Other equations. Integers. Mathematical reasoning & proof. Working systematically. Diophantine equations. Generalising. Games. Manipulating algebraic expressions/formulae. Simultaneous equations. Algebra - generally.
Published May 1999.
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