Sum of cubes of roots of a quartic equation $x^4 - 5x^2 + 2x -1= 0$
What is the sum of cube of the roots of equation other than using substitution method? Is there any formula to find the sum of square of roots, sum of cube of roots, and sum of fourth power of roots for quartic equation?

x^4=5x^2-2x+1
x^3=5x-2+(1/x)
Apply summation on both sides 
Let the roots be a,b,c,d
We know the value of a+b+c+d and 
1/a+1/b+1/c+1/d= (sum of roots taken 3 at a time)/ABCD
