Question

Найдите значение выражения$sqrt{25+4 sqrt{21} }$ + $sqrt{70-14 sqrt{21} }$

Answer 1

$sqrt{25+4sqrt{21}} + sqrt{70-14sqrt{21}} \ 1) sqrt{21+2*2sqrt{21} +4} = sqrt{(sqrt{21} +2)^2} = sqrt{21} + 2 \ 2) sqrt{49-2*7sqrt{21} + 21} = sqrt{ (7-sqrt{21})^2 } = 7 - sqrt{21} \ sqrt{21}+2+7-sqrt{21}=9$