for F being non 2 -characteristic Field
for a being non zero Element of F
for b, c, w being Element of F st w ^2 = (b ^2) - ((4 '*' a) * c) holds
( eval (<%c,b,a%>,(((- b) + w) * ((2 '*' a) "))) = 0. F & eval (<%c,b,a%>,(((- b) - w) * ((2 '*' a) "))) = 0. F )