1) 103² = (100+3)² = 10000+600+9 = 10609.
2) 99² = (100-1)² = 10000-200+1 = 9801.
3) 78² = (100-22)² = 10000-4400+484 = 6084.
4) 10,5² = (10+0,5)² = 100+10+0,25 = 110,25.
5) 5,1² = (5+0,1)² = 25+1+0,01 = 26,01.
6) 10,2² = (10+0,2)² = 100+4+0,04 = 104,04.