<=>3\(\sqrt{2x}\)-20\(\sqrt{2x}\)+21\(\sqrt{2x}\)=28
<=>4\(\sqrt{2x}\)=28
<=>\(\sqrt{2x}\)=7
<=>2x=14
<=>x=7
\(3\sqrt{2x}-5\sqrt{8x}+7\sqrt{18x}=28\)
\(3\sqrt{2x}-5\sqrt{8}.\sqrt{x}+7\sqrt{18x}=28\)
\(3\sqrt{2x}-5.2\sqrt{2}.\sqrt{x}+7\sqrt{18x}=28\)
\(3\sqrt{2x}-5.2\sqrt{2}.\sqrt{x}+7.\sqrt{18}.\sqrt{x}=28\)
\(3\sqrt{2x}-5.2\sqrt{2}.\sqrt{x}+7.3\sqrt{2}.\sqrt{x}=28\)
\(3\sqrt{2x}-5.2\sqrt{2x}+7.3\sqrt{2x}=28\)
\(3\sqrt{2x}-10\sqrt{2x}+21\sqrt{2x}=28\)
\(14\sqrt{2x}=28\)
\(392x=784\)
\(x=\frac{784}{392}=2\)
