2a²+2b²+2c²=2ab+2bc+2ca
(a-b)^2+(b-c)^2+(a-c)^2=0
a-b=0,a-c=0,b-c=0
a=b=c
a+2b+3c=12
a=b=c=2
a+b^2+c^3=2+4+8=14