BĐT cần chứng minh tương đương:
\(2x+\sqrt{12-2x^2}\le6\)
\(\Leftrightarrow\sqrt{12-2x^2}\le6-2x\)
\(\Rightarrow12-2x^2\le\left(6-2x\right)^2\)
\(\Leftrightarrow12-2x^2\le36-24x+4x^2\)
\(\Leftrightarrow6x^2-24x+24\ge0\)
\(\Leftrightarrow6\left(x-2\right)^2\ge0\left(\forall x\right)\)
Dấu "=" xảy ra khi: \(x-2=0\Rightarrow x=2\)