√﹙3√3＋6﹚＝√[﹙12＋6√3﹚/2]
＝√[3²＋2×3×√3＋﹙√3 ﹚²]/√2
＝﹙3＋√3﹚/√2
＝﹙3√2＋√6﹚/2.