Question

(2корень6-5) ^2-10корень(49-20корень6)

Answer 1

$(2sqrt{6}-5) ^2-10sqrt{49-20sqrt{6}}=(2sqrt{6}-5) ^2-10sqrt{(5-2sqrt{6})^2}=\=(2sqrt{6}-5) ^2-10|5-2sqrt{6}|=(5-2sqrt{6}) ^2-10(5-2sqrt{6})=\=(5-2sqrt{6})(5-2sqrt{6}-10)=-(5^2-(2sqrt{6})^2)=-1$