Question

1.Aratati ca numarul a= $\sqrt{1+3+5+.....+99}$ este rational
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2. a) $\frac{[(12 \frac{1}{12}+ \frac{1}{10} + \frac{4}{5} ): \frac{1}{15} -6: \frac{1}{28} ]x \frac{1}{4} }{(5x2 \frac{2}{5} -8 \frac{3}{22} ):42 \frac{1}{2} }$

Answer 1

forma generala a unui nr impar este 2k-1=99 rezulta de aici ca : k=50, deciconform formulei1+3+5+...+(2k-1)=k²⇒radical mare din 1+3+5+...+99=√50²=50∈Q