tìm x biết \(x^2=\frac{25}{36}\)
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S = 1/4 + 1/42 + 1/43 + ... + 1/450
4S = 4(1/4 + 1/42 + 1/43 + ... + 1/450)
4S = 1 + 1/4 + 1/42 + ... + 1/449
4S - S = (1 + 1/4 + 1/42 + ... + 149) - (1/4 + 1/42 + 1/43 + ... + 1/450)
3S = 1 - 1/450
S = \(\frac{1-\frac{1}{4^{50}}}{3}\)
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gọi 2 số là a,b
\(a\times b=112\)
Mà \(\left(a+2\right)\times b=126\)\(\Rightarrow\)mk ko bt :V
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\(1+\frac{1+\frac{2}{2}}{1+\frac{2}{3}}=1+\frac{2}{1+\frac{2}{\frac{5}{3}}}=1+\frac{2}{1+2\cdot\frac{3}{5}}\)
\(=1+\frac{2}{1+\frac{6}{5}}=1+\frac{2}{\frac{11}{5}}=1+2\cdot\frac{5}{11}=1+\frac{10}{11}\)
\(=\frac{21}{11}\)
\(1+\frac{1+\frac{2}{2}}{1+\frac{2}{3}}\)
\(=1+\frac{2}{\frac{5}{3}}\)
\(=1+\frac{6}{5}\)
\(=\frac{11}{5}\)
![](https://rs.olm.vn/images/avt/0.png?1311)
\(\frac{1999\times2001-1}{1999+1999\times2000}\times\frac{7}{5}\)
\(=\frac{2001-1}{1999\times2000}\times\frac{7}{5}\)
\(=\frac{2000}{1999\times2000}\times\frac{7}{5}\)
\(=1999\times\frac{7}{5}\)
........... còn lại tự xử lý nha
\(x^2=\frac{25}{36}\)
\(\Rightarrow x^2=\left(\frac{5}{6}\right)^2\)
\(\Rightarrow x=\frac{5}{6}\)
~ Hok tốt ~
\(x^2=\frac{25}{36}\)
\(\Rightarrow\orbr{\begin{cases}x=\frac{5}{6}\\x=\frac{-5}{6}\end{cases}}\)
Vậy \(x\in\left\{\frac{5}{6};\frac{-5}{6}\right\}\)