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Calculati: a) (x-3)(x+3)-(x+3)^2+3(2x+7)

Răspuns :

(x-3)(x+3) = x^2 - 9

(x+3)^2 = x^2 + 6x + 9

3(2x+7) = 6x + 21

x^2 - 9 - x^2 - 6x - 9 + 6x + 21 = 3