### 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?

### How Many Solutions?

Find all the solutions to the this equation.

### On the Road

Four vehicles travelled on a road. What can you deduce from the times that they met?

# More Parabolic Patterns

##### Stage: 4 and 5 Challenge Level:

We have received solutions from Sarah (Madras College, St Andrews), Andrei (School no. 205, Bucharest, Romania) and from Ryan and Belinda (Riccarton High School, Christchurch, New Zealand). Well done to you all.

All approached the problem in a similar way. Ryan and Belinda's response follows:

#### To get the lines curving downward from the top

We are given the equation for the middle curve (that goes through the point $(0,0)$) which is $y=x^2$. From there we add or subtract $2$ to give the curves going through the points $(0,2)$ and $(0,-2)$ respectively, giving the equations -

#### To get the lines curving upward from the bottom

This is a reflection of the downward curves, so we use opposite equations, e.g. instead of $y=x^2$we use $y=-x^2$. From there we add or subtract $2$ to give the curves going through the points $(0,2)$ and $(0,-2)$ respectively, giving the equations -

#### To get the lines curving from right to left

We are given the equation for the middle curve (that goes through the point $(0,0)$) which is $x=y^2$. From there we add or subtract $2$ to give the curves going through the points $(2,0)$ and $(-2,0)$ respectively, giving the equations -

#### To get the lines curving from left to right

This is a reflection of the right to left curves, so we use opposite equations, e.g. instead of $x=y^2$we use $x=-y^2$. From there we add or subtract $2$ to give the curves going through the points $(2,0)$ and $(-2,0)$ respectively, giving the equations -