Q.
Let a,b,c be any real numbers. Suppose that there are real numbers x,y,z not all zero such that x=cy+bz,y=az+cx and z=bx+ay then a2+b2+c2+2abc is equal to
The equation system x−cy−bz=0 cx−y+az=0 bx+ay−z=0
have non trivial solution if ∣∣1cb−c−1a−ba−1∣∣=0 Expand by R1,1(1−a2)+c(−c−ab)−b(ac+b)=0 1−a2−c2−abc−abc−b2=0 a2+b2+c2+2abc=1