"The accuracy must be not less than 10^-6"
i think we must replace 1 with 1.000000

how to output roots? "%lf"? "%0.6lf"?
and, there is an complex roots?

this means, that you can use any output format, but the difference between your answer and correct answer should not be greater then  10^-6

so easy:)

read the statement!
"Output all real roots of the polynomial..."