Question

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Answer 1

Răspuns:

$\frac{1}{1 \times 2} + \frac{1}{2 \times 3} + \frac{1}{3 \times4 } = \frac{1}{2} + \frac{1}{6} + \frac{1}{12} = \frac{6}{12} + \frac{2}{12} + \frac{1}{12} = \frac{9}{12} = \frac{3}{4}$

Answer 2

Răspuns:

$\frac{1}{2 \times 1} + \frac{1}{2 \times 3} + \frac{1}{3 \times 4} \\ = \frac{1}{2} + \frac{1}{6} + \frac{1}{12} \\ \\ amplificam \: cu \: 6 \: \: cu \: 2 \: si \: ultima \: ramane \: asa \\ \\ \frac{6}{12} + \frac{2}{12} + \frac{1}{12} \\ = \frac{9}{12} \: simplificam \: cu \: 3 = > \frac{3}{4}$