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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?

Polynomial Relations

Given any two polynomials in a single variable it is always possible to eliminate the variable and obtain a formula showing the relationship between the two polynomials. Try this one.

More Polynomial Equations

Find relationships between the polynomials a, b and c which are polynomials in n giving the sums of the first n natural numbers, squares and cubes respectively.

Janusz Asked

Age 16 to 18
Challenge Level
Start with the linear polynomial: $y = -3x + 9$. The $x$-coefficient, the root and the intercept are -3, 3 and 9 respectively, and these are in arithmetic progression. Are there any other linear polynomials that enjoy this property?

What about quadratic polynomials? That is, if the polynomial \[y = ax^2 + bx + c\] has roots $r_1$ and $r_2,$ can $a$, $r_1$, $b$, $r_2$ and $c$ be in arithmetic progression?

[The idea for this problem came from Janusz Kowalski of the Kreator Project.]