Question

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Очень срочно, помогите

Answer 1

$3sqrt{frac{7}{3}}+sqrt{84}-4sqrt{6,25}-sqrt{21}=sqrt{3^2cdotfrac{7}{3}}+sqrt{4cdot21}-sqrt{4^2cdot6frac{1}{4}}-sqrt{21}=\\=sqrt{3cdot7}+sqrt{2^2cdot21}-sqrt{4cdot25}-sqrt{21}=sqrt{21}+2sqrt{21}-sqrt{100}-sqrt{21}=\\=2sqrt{21}-10=2(sqrt{21}-5).$