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[tex]b = \frac{ \sqrt{13 ^{2}-5 ^{2} } }{ \sqrt{10 ^{2} -8 ^{2} } } b=?
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Răspuns :

[tex]b= \frac{ \sqrt{(13+5)(13-5)} }{ \sqrt{(10+8)(10-8)} } = \frac{ \sqrt{18*8} }{ \sqrt{18*2} } = \frac{ \sqrt{18}* \sqrt{8} }{ \sqrt{18}* \sqrt{2} }= \frac{ \sqrt{8} }{ \sqrt{2} }= \frac{ \sqrt{2*4} }{ \sqrt{2} }= \frac{ \sqrt{2}* \sqrt{4} }{ \sqrt{2} }= \sqrt{4}=2 [/tex]