[질문] 근의공식증명

전개해보면x²+ax+(a/4)²-(a/4)²+b=(x+(a/2))²-(a/4)²+b=0(x+(a/2))²=(a/4)²+b요기서루트씌워주면(x+(a/2))=+-루트{(a/4)²+b}P따라서x=-(a/2)+-루트{(a/4)²+b}