### Real(ly) Numbers

If x, y and z are real numbers such that: x + y + z = 5 and xy + yz + zx = 3. What is the largest value that any of the numbers can have?

### Roots and Coefficients

If xyz = 1 and x+y+z =1/x + 1/y + 1/z show that at least one of these numbers must be 1. Now for the complexity! When are the other numbers real and when are they complex?

### Pair Squares

The sum of any two of the numbers 2, 34 and 47 is a perfect square. Choose three square numbers and find sets of three integers with this property. Generalise to four integers.

# System Speak

##### Age 16 to 18 Challenge Level:

Take a look at the system of equations below:

$ab = 1$

$bc = 2$

$cd = 3$

$de = 4$

$ea = 6$

Can you find a set of values {a, b, c, d, e} that satisfy the system?
Can you find more than one?