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:
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 -
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 -
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 -
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 -