 Elementary algebra provides finite ways of managing the infinite. A formula such as \(\pi r^2\) for the area of a circle of radius \(r\) describes infinitely many possible computations, one for each possible valuation of its variables. A universally true law expresses infinitely many cases, for example the single equation \(x+y = y+x\) summarizes the infinitely many facts \(1+2 = 2+1, 3+7 = 7+3\), etc. The equation \(2x = 4\) selects one number from an infinite set of possibilities. And \(y = 2x+3\) expresses the infinitely many points of the line with slope 2 passing through \((0, 3)\) with a finite equation whose solutions are exactly those points.