Giải câu 3 trang 21 sách phát triển năng lực toán 9 tập 1

a) $\sqrt{50}:\sqrt{18}$ = $\frac{\sqrt{50}}{\sqrt{18}}=\frac{\sqrt{25.2}}{\sqrt{9.2}}=\frac{\sqrt{25}.\sqrt{2}}{\sqrt{9}.\sqrt{22}}=\frac{\sqrt{25}}{\sqrt{9}}=\frac{5}{3}$

b) $\sqrt{\frac{7}{6}}$ : $\sqrt{\frac{14}{9}}$ = $\sqrt{\frac{7}{6}:\frac{14}{9}}$ = $\sqrt{\frac{7}{6}.\frac{9}{14}}$ = $\sqrt{\frac{3}{4}}$ = $\frac{\sqrt{3}}{\sqrt{4}}=\frac{\sqrt{3}}{2}$

c) $(7\sqrt{32}+3\sqrt{18}-2\sqrt{8}):\sqrt{2}$ = $7\frac{\sqrt{32}}{\sqrt{2}}+3\frac{\sqrt{18}}{\sqrt{2}}-2\frac{\sqrt{8}}{\sqrt{2}}$

   = $7\sqrt{\frac{32}{2}}+3\sqrt{\frac{18}{2}}-2\sqrt{\frac{8}{2}}=7\sqrt{16}+3\sqrt{9}-2\sqrt{4}$

   = 7.4 + 3.3 - 2.2 = 33

d) $\frac{\sqrt{18}}{\sqrt{2}}-\frac{\sqrt{12}}{\sqrt{3}}$ = $\sqrt{\frac{18}{2}}-\sqrt{\frac{12}{3}}=\sqrt{9}-\sqrt{4}=3-2=1$