Tolong jelaskan bagaimana cara mencari panjang AD

L = 84 cm^2; panjang AB = 3√3+√6 cm

L= p × l
84 = (3√3+√6) x l
l = [tex] \frac{84}{3 \sqrt{3} + \sqrt{6} } [/tex] (dirasionalkan)
l = [tex] \frac{84}{3 \sqrt{3}+ \sqrt{3} } [/tex] × [tex] \frac{3 \sqrt{3} - \sqrt{6} }{3 \sqrt{3} - \sqrt{6} } [/tex]
l = [tex] \frac{84(3 \sqrt{3} - \sqrt{6} )}{(9.3)-6} [/tex]
l = [tex] \frac{84(3 \sqrt{3}- \sqrt{6} )}{27-6} [/tex]
l = [tex] \frac{84(3 \sqrt{3}- \sqrt{6} )}{21} [/tex] (84÷21=4)
l = [tex]4(3 \sqrt{3}- \sqrt{6} )[/tex] 

l = AD = [tex]4(3 \sqrt{3}- \sqrt{6} )[/tex] cm (b)

semoga membantu ^^