2a²+2b²+2c²+2ab+2bc+2ac=(a+b)²+(b+c)²+(c+a)²
2a²+2b²+2c²+2ab -2bc -2ac=(a+b)²+(b -c)²+(c -a)²
2a²+2b²+2c² -2ab+2bc+2ac=(a -b)²+(b+c)²+(c+a)²
2a²+2b²+2c² -2ab+2bc -2ac=(a -b)²+(b+c)²+(c -a)²
2a²+2b²+2c² -2ab -2bc+2ac=(a -b)²+(b -c)²+(c+a)²
2a²+2b²+2c² -2ab -2bc -2ac=(a -b)²+(b -c)²+(c -a)²