Răspuns:
[tex]l) \frac{x}{x + 1} + \frac{1}{x + 1} = \frac{x + 1}{x + 1} = 1 \\ m) \frac{y + 1}{y + 3} + \frac{3}{y + 3} + \frac{y + 2}{y + 3} = \frac{y + 1 + 3 + y + 2}{y + 3} = \frac{(2y + 6)}{(y + 3)} = 2 \\ n) \frac{2}{n + 1} + \frac{4}{n + 1} +... + \frac{2n}{n + 1} = \frac{2 + 4 + ... + 2n}{n + 1} = \frac{2(1 + 2 + ... + n)}{n + 1} = \frac{2n(n + 1) \div 2}{n + 1} = \frac{n(n + 1)}{n + 1} = \frac{n}{1} = 1 [/tex]
