Hilbert’s 16th problem is an expansion of grade school graphing questions. An equation of the form ax + by = c is a line; an equation with squared terms is a conic section of some form — parabola, ellipse or hyperbola. Hilbert sought a more general theory of the shapes that higher-degree polynomials could have. So far the question is unresolved, even for polynomials with the relatively small degree of 8.
The Formula to Get 42 Billion Digits of π
While writing "7 Utterly Well-written Math Books About Pi," I found a very interesting math formula that will give you 42 consecutive digits of π accurately but is still wrong.