Question

giup em cau a va c voi

Answer 1

a) Giả sử \(2\sqrt{2}+1< 10\)

\(\Leftrightarrow2\sqrt{2}< 9\)

\(\Leftrightarrow\left(2\sqrt{2}\right)^2< 9^2\)

\(\Leftrightarrow8< 81\left(đúng\right)\)

Vậy \(2\sqrt{2}+1< 10\)

b) Giả sử \(2-\sqrt{10}>-1\)

\(\Leftrightarrow3>\sqrt{10}\)

\(\Leftrightarrow3^2>\left(\sqrt{10}\right)^2\)

\(\Leftrightarrow9>10\left(sai\right)\)

Vậy \(2-\sqrt{10}< -1\)

c) Giả sử \(5-2\sqrt{3}< 1\)

\(\Leftrightarrow4< 2\sqrt{3}\)

\(\Leftrightarrow4^2< \left(2\sqrt{3}\right)^2\)

\(\Leftrightarrow16< 12\left(sai\right)\)

Vậy \(5-2\sqrt{3}>1\)

Answer 2

a.

\(2\sqrt{2}+1=\sqrt{8}+1< \sqrt{9}+1=4< 10\)

Vậy \(2\sqrt{2}+1< 10\)

c.

\(5-2\sqrt{3}=5-\sqrt{12}>5-\sqrt{16}=1\)

Vậy \(5-2\sqrt{3}>1\)