Đáp án:
2)a, $\frac{3}{4}$
b, 8
3) 2 - $\sqrt[]{3}$
Giải thích các bước giải:
2) a, $\sqrt[]{45}$ : $\sqrt[]{80}$ = $\sqrt[]{\frac{45}{80}}$
= $\sqrt[]{\frac{9}{16}}$ = $\sqrt[]{\frac{3^2}{4^2}}$ = $\frac{3}{4}$
b, ($\sqrt[]{18}$ + $\sqrt[]{8}$ - $\sqrt[]{2}$).$\sqrt[]{2}$
= $\sqrt[]{18}$.$\sqrt[]{2}$ + $\sqrt[]{8}$.$\sqrt[]{2}$ - $\sqrt[]{2}$.$\sqrt[]{2}$
= $\sqrt[]{18.2}$ + $\sqrt[]{8.2}$ - $\sqrt[]{2.2}$
= $\sqrt[]{36}$ + $\sqrt[]{16}$ - $\sqrt[]{4}$
= 6 + 4 - 2 = 8
3) $\frac{1}{\sqrt[]{3}+2}$ = $\frac{\sqrt[]{3}-2}{(\sqrt[]{3}+2).(\sqrt[]{3}-2})$
= $\frac{\sqrt[]{3}-2}{3-4}$ = 2 - $\sqrt[]{3}$
