a) Ta có: \(a+b+\frac{1}{2}\ge\sqrt{a}+\sqrt{b}+\sqrt{\frac{1}{2}}>\sqrt{a}+\sqrt{b}\)
Dấu "=" không xảy ra
b) Ta có: \(\frac{\sqrt{a}+\sqrt{b}}{\sqrt{2}}>\sqrt{\frac{a+b}{2}}=\frac{\sqrt{a+b}}{\sqrt{2}}\ge\frac{\sqrt{a}+\sqrt{b}}{2}\)
Dấu "=" xảy ra khi a = b