a*a+b*b+c*c+26=2a+6b+8c
a^2+b^2+c^2-2a-6b-8c+26=0
(a-1)^2+(b-3)^2+(c-4)^2=0
a-1=0 b-3=0 c-4=0
a=1 b=2 c=4
abc/(a^2+b^2-c^2)=1*3*4/(1^2+3^2-4^2)=-2
a*a+b*b+c*c+26=2a+6b+8c
a^2+b^2+c^2-2a-6b-8c+26=0
(a-1)^2+(b-3)^2+(c-4)^2=0
a-1=0 b-3=0 c-4=0
a=1 b=2 c=4
abc/(a^2+b^2-c^2)=1*3*4/(1^2+3^2-4^2)=-2