315. Solve the system of equations: $x-y=a ; x y=b$.

## Problems from "Coss" by Rudolf in the adaptation by Stifel.
315. Rudolf's Solution: from the first equation $x=a+y$; substituting into the second, we get: $y(a+y)=b ; y^{2}+a y-b=0$.

Rudolf's "Coss" was processed and supplemented by Stifel (see below) in 1552.