Đáp án:
`A`
Giải thích các bước giải:
`\qquad {\sqrt{12-2\sqrt{35}}+\sqrt{6-2\sqrt{5}}}/\sqrt{8+2\sqrt{7}}`
`={\sqrt{7-2\sqrt{7}.\sqrt{5}+5}+\sqrt{5-2\sqrt{5}.1+1^2}}/\sqrt{7+2\sqrt{7}.1+1^2}`
`={\sqrt{(\sqrt{7}-\sqrt{5})^2}+\sqrt{(\sqrt{5}-1)^2}}/{(\sqrt{7}+1)^2}`
`={|\sqrt{7}-\sqrt{5}|+|\sqrt{5}-1|}/|\sqrt{7}+1|`
`={\sqrt{7}-\sqrt{5}+\sqrt{5}-1}/{\sqrt{7}+1}`
`={(\sqrt{7}-1)(\sqrt{7}-1)}/{(\sqrt{7}+1)(\sqrt{7}-1)}`
`={7-2\sqrt{7}+1}/{7-1}={8-2\sqrt{7}}/6`
`={4-\sqrt{7}}/3=4/3-1/3\sqrt{7}=a+b\sqrt{7}`
`=>`$\begin{cases}a=\dfrac{4}{3}\\b=\dfrac{-1}{3}\end{cases}$
`=>a+b=4/3+(-1/3)=1`
Đáp án $A$
