Question

$(-2/ sqrt{5}) ^{2} +(1/ sqrt{5} ) ^{2}$$=1$
Объясните как!

Answer 1

$(- frac{2}{ sqrt{5}})^2+(frac{1}{ sqrt{5}})^2=1 \ frac{2^2}{( sqrt{5})^2}+frac{1^2}{( sqrt{5})^2}=1 \ frac{4}{5}+ frac{1}{5}=1 \ frac{5}{5}=1 \ 1=1$