We have
1d^6 - 6d^5*(5y) + 15d^4*(5y)^2 - 20d^3*(5y)^3 + 15d^2(5y)^4 - 6d*(5y)^5 + 1(5y)^6
d^6 - 30d^5y + 375d^4y^2 - 2500d^3y^3 + 9375d^2y^3 - 18750dy^5 + 15625y^6
x^4 - 6x^2 - 7x - 6 = 0
Using the Rational roots Theorem, 3 is a root....
Using synthetic division to find the remaining polynomial, we have
3 [ 1 0 -6 - 7 - 6 ]
3 9 9 6
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1 3 3 2 0
So we have
x^3 + 3x^2 + 3x + 2 and we can write
x^3 + 3x^2 + 2x + x + 2 factor
x ( x^2 + 3x + 2) + 1 (x + 2)
x (x + 2)(x + 1) + 1 ( x + 2)
(x + 2) [ x(x + 1) + 1 ]
(x + 2) [ x^2 + x + 1]
So -2 is the other real root
And using the quadratic formula....the roots of the other polynomial are
[-1 ± i√3] / 2
