if a,b,c are roots of x^3+4x+1=0,then (a+b)^-1+(b+c)^-1+(c+a)^-1=

Hi,

Write the 2^nd equation and take the LCM. Now analyze the nemberator and denominator. You will see that in both numberator and denominator sum of roots, sum of roots taken two at a time and product of the roots forming.

Substitute the values to get the answer.