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Fie
[tex]a = ( \sqrt{2} + \sqrt{8} + \sqrt{18} - \sqrt{50} ) \times ( \frac{1}{ \sqrt{2} } - \frac{1}{ \sqrt{8} } - \frac{1}{ \sqrt{32} }) [/tex]
Efectuând calculele obtinem pentru numarul A:
[tex]a) \frac{1}{ \sqrt{2} } \\ b) \frac{1}{4} \\ c) \frac{ \sqrt{2} }{4} \\ d) - \frac{ \sqrt{2} }{2} [/tex]


Răspuns :

Răspuns:

[tex]{ \red{b) \: \frac{1}{4} }}[/tex]

Explicație pas cu pas:

[tex]( \sqrt{2} + \sqrt{8} + \sqrt{18} - \sqrt{50} ) \times ( \frac{1}{ \sqrt{2} } - \frac{1}{ \sqrt{8} } - \frac{1}{ \sqrt{32} } ) \\ ( \sqrt{2} + 2 \sqrt{2} + 3 \sqrt{2} - 5 \sqrt{2} ) \times ( \frac{1}{ \sqrt{2} } - \frac{1}{2 \sqrt{2} } - \frac{1}{4 \sqrt{2} } ) \\ \sqrt{2} ( {}^{4)} \frac{1}{ \sqrt{2} } - {}^{2)} \frac{1}{2 \sqrt{2} } - \frac{1}{4 \sqrt{2} } ) \\ \sqrt{2}( \frac{4}{4 \sqrt{2} } - \frac{2}{4 \sqrt{2} } - \frac{1}{4 \sqrt{2} } ) \\ \sqrt{2} \times \frac{1}{4 \sqrt{2} } = { \red{ \frac{1}{4} }} = > varianta \: corecta \: { \red{b)}}[/tex]

Succes!

[tex]\bf a=(\sqrt2+\sqrt8+\sqrt{18}-\sqrt{50})\cdot\bigg(\dfrac{1}{\sqrt2}-\dfrac{1}{\sqrt8}-\dfrac{1}{\sqrt{32}}\bigg)=\\ \\ \\ =\sqrt2(1+2+3-5)\cdot\bigg(\dfrac{1}{\sqrt2}-\dfrac{1}{\sqrt8}-\dfrac{1}{\sqrt{32}}\bigg)=\sqrt2\cdot\bigg(\dfrac{1}{\sqrt2}-\dfrac{1}{\sqrt8}-\dfrac{1}{\sqrt{32}}\bigg)=\\ \\ \\ =1-\dfrac{1}{2}-\dfrac{1}{4}=\dfrac{1}{4}[/tex]