ПОВТОРЮЄМО АЛГЕБРУ ЗА 8 КЛАС: 49

49. Скоротіть дріб:

1) $\frac{a+5\sqrt{a}}{a-258}$ = $\frac{\sqrt{a}(\sqrt{a}+5)}{(\sqrt{a}-5)(\sqrt{a}+5)}$ = $\frac{\sqrt{a}}{\sqrt{a}-5}$;

2) $\frac{x-4y}{x+4\sqrt{x}\sqrt{y}+4y}$ = $\frac{(\sqrt{x}-2\sqrt{y})(\sqrt{x}+2\sqrt{y})}{{(\sqrt{x}+2\sqrt{y})}^2}$ = $\frac{\sqrt{x}-2\sqrt{y}}{\sqrt{x}+2\sqrt{y}}$;

3) $\frac{\sqrt{21}-3}{7-\sqrt{21}}$ = $\frac{\sqrt{3}•\sqrt{7}-(\sqrt{3}{)}^2}{(\sqrt{7}{)}^2-\sqrt{3}•\sqrt{7}}$ = $\frac{\sqrt{3}(\sqrt{7}-\sqrt{3})}{\sqrt{7}(\sqrt{7}-\sqrt{3})}$ = $\sqrt{\frac{3}{7}}$;