/ ______________\ / ______________\ / ____________\ / ____________\ | / ____ | | / ____ | | / ____ | | / ____ | | / 1 \/ 21 | | / 1 \/ 21 | | / 1 \/ 21 | | / 1 \/ 21 | |x + I* / - - + ------ |*|x - I* / - - + ------ |*|x + / - + ------ |*|x - / - + ------ | \ \/ 2 2 / \ \/ 2 2 / \ \/ 2 2 / \ \/ 2 2 /
(((x + i*sqrt(-1/2 + sqrt(21)/2))*(x - i*sqrt(-1/2 + sqrt(21)/2)))*(x + sqrt(1/2 + sqrt(21)/2)))*(x - sqrt(1/2 + sqrt(21)/2))