1) a) $\sqrt{12}$ + 3$\sqrt{48}$ - 5$\sqrt{75}$
= 2$\sqrt{3}$ + 3.4$\sqrt{3}$ - 5.5$\sqrt{3}$
= (2 + 3.4 - 5.5).$\sqrt{3}$
= -11$\sqrt{3}$
b)5`\sqrt{1/5}` - $\frac{8}{1+\sqrt{5}}$ + $\frac{\sqrt{20}-5}{2-\sqrt{5}}$
= `\sqrt{5}` - (-2 + 2`\sqrt{5}`) + `\sqrt{5}`
= 2
2) a)$\sqrt{9x^2}$ = 6
`<=>` 9$x^{2}$ = 36
`<=>` $x^{2}$ = 4
`<=>` $\left[\begin{matrix} x=2\\ x= -2\end{matrix}\right.$
b)$\sqrt{4x-20}$ + $\sqrt{x-5}$ - $\frac{1}{3}$$\sqrt{9x-45}$ = 4
`<=>` 4$\sqrt{x-5}$ + $\sqrt{x-5}$ - $\frac{1}{3}$.9.$\sqrt{x-5}$ = 4
`<=>` (4 + 1 - 3).$\sqrt{x-5}$ = 4 `<=>` 2.$\sqrt{x-5}$ = 4
`<=>` $\sqrt{x-5}$ = 2
`<=>` x - 5 = 4
`<=>` x = 9
