Question

|5-2корень7|*(5-2корень7)-20 корней 7

Answer 1

$|5-2 sqrt{7}|(5-2 sqrt{7})-20 sqrt{7}=-(5-2 sqrt{7})(5-2 sqrt{7})-20 sqrt{7}=\\=-(5^2-(2 sqrt{7})^2)-20 sqrt{7}=-25+4*7-20 sqrt{7}=\\=-25+28-20 sqrt{7}=3-20 sqrt{7}$