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Răspuns:
[tex] {x}^{2} + 6x + 7 = {x}^{2} + 6x + 9 - 2 = \\ = {x}^{2} + 2 \times x \times 3 + {3}^{2} - 2 = {(x + 3})^{2} - 2[/tex]