Explicație pas cu pas:
[tex]a \binom{3}{x} = \frac{x! }{(x - 3)! } = \\ \frac{(x - 3)! (x - 2)(x - 1)x}{(x - 3)! } = \\ x(x - 2)(x - 1) \\ c\binom{x - 2}{x} = \frac{x! }{(x - 2)! (x - x + 2)! } = \\ \frac{(x - 2)! (x - 1)x}{(x - 2)! 2} = \frac{x(x - 1)}{2} \\ (x - 2)(x - 1)x + \frac{(x - 1)x}{2} = 14x \\ (x - 1)(2x - 4 + 1) = 7 \\ (x - 1)(2x - 3) = 7 \\ (x - 1) = 7= > x1 = 8 \\ (2x - 3) = 7 = > x2 = 5[/tex]
