Răspuns:
[tex]e(x) = (3x + 4) ^{2} - (2x + 1)^{2} \\ = 3 {x}^{2} + 3x \times 2 \times 4 + {4}^{2} - 2 {x}^{2} - 2 \times 2x \times 1 - {1}^{2} \\ = 9 {x}^{2} + 24x + 16 - 4 {x}^{2} - 4x - 1 \\ = 5 {x}^{2} + 20x - 15 \\ [/tex]
[tex]5 {x}^{2} + 20x - 15 = > x(5x + 20 - 15) = > x(5x + 5)[/tex]
