Question

(Корень из 5 -2)^2*(9+4 корень из 5)-2корень из 5*4/5

Answer 1

$(sqrt5-2)^2cdot (9+4sqrt5)-2sqrt5cdot frac{4}{5}=\\=(5-4sqrt5+4)(9+4sqrt5)- frac{8sqrt5}{5}= \\=(9-4sqrt5)(9+4sqrt5)-frac{8sqrt5}{5}=\\=81-16cdot 5-frac{8sqrt5}{5}=81-80-frac{8sqrt5}{5}=1- frac{8sqrt5}{5} = frac{5-8sqrt5}{5}$