kill(all)$
load(ntrig)$
load(atrig1)$
fpprintprec:6;

van=facebook.com/LearningCalculus$

f(x):=x^4-4*x^2-4=x;

factor(f(x));

solutions:factor(radcan(solve(f(x),x)))$
solutions:subst(u,9*sqrt(21001)-1253, solutions)$
solutions:subst(k^2,u^(2/3),subst(k,u^(1/3), solutions))$
solutions:subst(k^(3/2),sqrt(u), solutions)$
solutions:subst(k^(1/2),u^(1/6), solutions)$

solutions[1];
solutions[2];
solutions[3];
solutions[4];

solutions:factor(radcan(solve(f(x),x)))$

float(solutions[3]);
float(solutions[4]);