Răspuns:
[tex](10 + 10 + 10) ^{2} = {10}^{2} + {10}^{2} + {10}^{2} + 2 \times 10 \times 10 + 2 \times 10 \times 10 + 2 \times 10 \times 10 \\ {30}^{2} = 300 + 200 + 200 + 200 = 900 \\ \\ {(2 + 3 + 4)}^{2} = {2}^{2} + {3}^{2} + {4}^{2} + 2 \times 2 \times 3 + 2 \times 3 \times 4 + 2 \times 4 \times 2 \\ {9}^{2} = 4 + 9 + 16 + 12 + 24 + 16 \\ \\ 81 = 81[/tex]