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Algebra Difficulty 5.2 AIME, harder Find the answer

Let z1,z2,z3,z4z_{1}, z_{2}, z_{3}, z_{4} be the solutions to the equation x4+3x3+3x2+3x+1=0x^{4}+3 x^{3}+3 x^{2}+3 x+1=0. Then z1+z2+z3+z4\left|z_{1}\right|+\left|z_{2}\right|+\left|z_{3}\right|+\left|z_{4}\right| can be written as a+bcd\frac{a+b \sqrt{c}}{d}, where cc is a square-free positive integer, and a,b,da, b, d are positive integers with gcd(a,b,d)=1\operatorname{gcd}(a, b, d)=1. Compute 1000a+100b+10c+d1000 a+100 b+10 c+d.

A number or a short expression. Fractions can be typed as 3/2, and spacing doesn't matter.

Solution

Note that x=0x=0 is clearly not a solution, so we can divide the equation by x2x^{2} to get (x2+2+1x2)+3(x+1x)+1=0\left(x^{2}+2+\frac{1}{x^{2}}\right)+3\left(x+\frac{1}{x}\right)+1=0. Letting y=x+1xy=x+\frac{1}{x}, we get that y2+3y+1=0y^{2}+3 y+1=0, so y=x+1x=3±52y=x+\frac{1}{x}=\frac{-3 \pm \sqrt{5}}{2}. Since 3+52\frac{-3+\sqrt{5}}{2} has absolute value less than 2, the associated xx are on the unit circle, and thus the two solutions for xx in this case each have magnitude 1. For 352\frac{-3-\sqrt{5}}{2}, the roots are negative reals that are reciprocals of each other. Thus, the sum of their absolute values is the absolute value of their sum, which is 3+52\frac{3+\sqrt{5}}{2}. Thus, the sum of the magnitudes of the four solutions are 1+1+3+52=7+521+1+\frac{3+\sqrt{5}}{2}=\frac{7+\sqrt{5}}{2}.

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Source: Omni-MATH, licensed Apache-2.0. Statement and solution reproduced as published; topic and difficulty added by this site.