2 câu trả lời
Đáp án:
Giải thích các bước giải:
$\sqrt{4+\sqrt7}-\sqrt{4-\sqrt7}=\sqrt2\left(\sqrt{4+\sqrt7}-\sqrt{4-\sqrt7}\right):\sqrt2\\=\left(\sqrt{8+2\sqrt7}-\sqrt{8-2\sqrt7}\right):\sqrt2\\=\left(\sqrt{7+2\sqrt7+1}-\sqrt{7-2\sqrt+1}\right):\sqrt2\\=\left(\sqrt{\left(\sqrt7+1\right)^2}-\sqrt{\left(\sqrt7-1\right)^2}\right):\sqrt2\\=\left(\left|\sqrt7+1\right|-\left|\sqrt7-1\right|\right):\sqrt2=\left(\sqrt7+1-\sqrt7+1\right):\sqrt2\\=2:\sqrt2 =\dfrac{2}{\sqrt{2}}=\dfrac{2\sqrt2}{2}=\sqrt{2}$
chúc em học tốt
Đáp án+Giải thích các bước giải:
`sqrt{4+sqrt7}-sqrt{4-sqrt7}`
`=sqrt2(sqrt{4+sqrt7}-sqrt{4-sqrt7}):sqrt2`
`=(sqrt{8+2sqrt7}-sqrt{8-2sqrt7}):sqrt2`
`=(sqrt{7+2sqrt7+1}-sqrt{7-2sqrt+1}):sqrt2`
`=(sqrt{(sqrt7+1)^2}-sqrt{(sqrt7-1)^2}):sqrt2`
`=(|sqrt7+1|-|sqrt7-1|):sqrt2`
`=(sqrt7+1-sqrt7+1):sqrt2`
`=2:sqrt2`
`=2/sqrt2`
`=(2sqrt2)/2`
`=sqrt2`