Đáp án:
Giải thích các bước giải:
a)4/√2+1 =4.(√2-1)/(√2-1).(√2+1)=4√2-4/2 -1=4√2 -4
c)$\frac{\sqrt[]{5}+3}{\sqrt[]{5}-3}$
=$\frac{(\sqrt[]{5}+3).(\sqrt[]{5}+3)}{(\sqrt[]{5}-3).(\sqrt[]{5}+3}$
=$\frac{(\sqrt[]{5}+3)²}{5-9}$
=$\frac{-(\sqrt[]{5}+3)²}{4}$
b)$\frac{3}{\sqrt[]{7}+4}$
=$\frac{3.(\sqrt[]{7}-4)}{(\sqrt[]{7}+4).(\sqrt[]{7}-4)}$
=$\frac{3.(\sqrt[]{7}-4)}{-9}$
=$\frac{4-\sqrt[]{7}}{3}$
d)$\frac{a}{\sqrt[]{2b}-3}$
=$\frac{a.(\sqrt[]{2b}+3)}{(\sqrt[]{2b}-3).(\sqrt[]{2b}+3)}$
=$\frac{a\sqrt[]{2b}+3a}{2b -9}$
e)$\frac{11}{2\sqrt[]{a}-1}$
=$\frac{11.(2\sqrt[]{a}-1)}{(2\sqrt[]{a}-1).(2\sqrt[]{a}+1)}$
=$\frac{22\sqrt[]{a}-11}{4a-1}$
