1) 2$\sqrt{3}$ - 4$\sqrt{27}$ + 5$\sqrt{48}$ - $\frac{2}{3}$$\sqrt{75}$
= 2$\sqrt{3}$ - 12$\sqrt{3}$ + 20$\sqrt{3}$ - $\frac{10}{3}$$\sqrt{3}$
= $\frac{20}{3}$$\sqrt{3}$
2) $\sqrt{15 + 4\sqrt{11}}$ + $\sqrt{(3 - \sqrt{11})²}$
= $\sqrt{11 + 4\sqrt{11} + 4}$ + |3 - $\sqrt{11}$|
= $\sqrt{(\sqrt{11} + 2)²}$ + $\sqrt{11}$ - 3
= |$\sqrt{11}$ + 2| + $\sqrt{11}$ - 3
= $\sqrt{11}$ + 2 + $\sqrt{11}$ - 3
= 2$\sqrt{11}$ - 1
3) 4x == -5
⇔ x = -$\frac{5}{4}$
Vậy x = -$\frac{5}{4}$
