If a + b + c = 0, a,b,c ϵ Q, then the roots of the equation (b+c−a)x2+(c+a−b)x+(a+b−c)=0 are :
Rational
Let A = b + c - a, B = c + a - b, C = a + b - c.
Then A+B+C = a + b + c = 0 and equation becomes
Ax2 + Bx + C = 0
D=B2−4AC=(C+A)2−4AC=(C−A)2 .
Therefore, D is perfect square and A,B,C are rational numbers, therefore roots are rational.