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subject ： Finding the root of a quadratic equation of one variable
describe ： Programming , Input from keyboard a、b、c Value ,
Calculate the root of a quadratic equation in one variable , And according to bb-4a*c The value is greater than 0、 be equal to 0、 Less than 0 Discuss separately .
requirement ：
Input format : Use three in turn input Input separately a、b、c Value .
Output format Output calculation results , Keep two decimal places
