Question

[d]

X×2 -10 (2/11×13 +2/13×15 + 2/15×17 + .... 2/53×55) = 3/11

Answer 1

[Không Tên]

\(2x-10\left(\frac{2}{11.13}+\frac{1}{13.15}+\frac{1}{15.17}+...+\frac{2}{53.55}\right)=\frac{3}{11}\)

\(\Leftrightarrow\)\(2x-10\left(\frac{1}{11}-\frac{1}{13}+\frac{1}{13}-\frac{1}{15}+...+\frac{1}{53}-\frac{1}{55}\right)=\frac{3}{11}\)

\(\Leftrightarrow\)\(2x-10\left(\frac{1}{11}-\frac{1}{55}\right)=\frac{3}{11}\)

\(\Leftrightarrow\)\(2x-\frac{8}{11}=\frac{3}{11}\)

\(\Leftrightarrow\)\(2x=1\)

\(\Leftrightarrow\)\(x=\frac{1}{2}\)

Answer 2

[lyna trang]

x=\(\frac{1}{2}\)

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