see also: Elf[?] (1971-1976), Rainbow (1974-1979), Black Sabbath (1979-1983; returns 1991) and Dio (1982-present)
Discography:
With Rainbow
With Black Sabbath
With Dio
... by a, we have <math> x^2 + \left( \frac{b}{a} \right) x + \frac{c}{a}=0 </math> which is equivalen ...