Tìm x biết : \(\sqrt{x+2}\)= \(\frac{5}{7}\)
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1.
= -(13 + 3 căn7 ) / 2 + -(7 + 3 căn7 ) / 2
= -7 + 3 căn7
![](https://rs.olm.vn/images/avt/0.png?1311)
\(\frac{x}{16}=\frac{2\sqrt{27+7\sqrt{5}}}{\sqrt{10}+7\sqrt{2}}\)
\(\Leftrightarrow\frac{x}{16}=\frac{\sqrt{54+14\sqrt{5}}}{\sqrt{5}+7}\)
\(\Leftrightarrow\frac{x}{16}=\frac{\sqrt{49+2.7.\sqrt{5}+5}}{\sqrt{5}+7}\)
\(\Leftrightarrow\frac{x}{16}=\frac{\sqrt{\left(\sqrt{5}+7\right)^2}}{\sqrt{5}+7}=\frac{\sqrt{5}+7}{\sqrt{5}+7}=1\)
\(\Leftrightarrow x=16\)
![](https://rs.olm.vn/images/avt/0.png?1311)
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\(đk:x\ge-2\)
\(\sqrt{x+2}=\frac{5}{7}\Leftrightarrow x+2=\frac{25}{49}\Leftrightarrow x=\frac{25}{49}-2=\frac{-73}{49}\left(n\right)\)
vậy \(x=\frac{-73}{49}\)
\(\sqrt{x+2}=\frac{5}{7}\)
\(\Rightarrow x+2=\frac{25}{49}\)
\(\Rightarrow x=\frac{25}{49}-2\)
\(\Rightarrow x=\frac{-73}{49}\)
Vậy, \(x=\frac{-73}{49}\)
![](https://rs.olm.vn/images/avt/0.png?1311)
\(\sqrt{x+2}\) = \(\frac{5}{7}\)
\(\Rightarrow\) x + 2 = \(\left(\frac{5}{7}\right)^2\)
\(\Rightarrow\) x + 2 = \(\frac{25}{49}\)
\(\Rightarrow\) x = \(\frac{25}{49}\) - 2
\(\Rightarrow\) x = \(\frac{-73}{49}\)
Vậy x = \(\frac{-73}{49}\)
\(\sqrt{x+2}=\frac{5}{7}\)
\(\Rightarrow x+2=\left(\frac{5}{7}\right)^2\)
\(\Rightarrow x+2=\frac{25}{49}\)
\(x=\frac{25}{49}-2=-\frac{73}{49}\)
\(\sqrt{x+2}=\frac{5}{7}\)
Đk:\(x\ge-2\)
Thấy 2 vế luôn dương, bình 2 vế ta có:
\(\sqrt{\left(x+2\right)^2}=\left(\frac{5}{7}\right)^2\)
\(\Leftrightarrow x+2=\frac{25}{49}\)
\(\Leftrightarrow x=-\frac{73}{49}\left(tm\right)\)
x+2 = 25/49
x= -73/49