引用第22樓朗仔於2010-04-01 17:51發表的“”: ax^2+2bx+c=0 has two equal real roots, which of the following is/ara true? I. both roots are -b/a II. a,b,c form a geometric progression III. a,b,c form an arithmetic progresion .......
delta = 0 4b^2 - 4ac = 0 b^2 -ac = 0 b^2 = ac
by definition, II is correct
delta =0 roots = -2b\2a = -b/a |