1/2 - 1/2.(3-2x)=0 ( dấu gạch chéo là phân số nha)
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Phép tính trên bằng: \(\frac{1}{2}.\left(\frac{1}{3}-\frac{1}{5}+\frac{1}{5}-\frac{1}{7}+...+\frac{1}{2x+1}-\frac{1}{2x+3}\right)=\frac{1}{2}\left(\frac{1}{3}-\frac{1}{2x+3}\right)=\frac{x}{6x+9}\)
Bài làm:
\(\left(\frac{1}{1.3}+\frac{1}{3.5}+\frac{1}{5.7}+\frac{1}{7.9}+\frac{1}{9.11}\right).y=\frac{2}{3}\)
\(\Leftrightarrow\left(\frac{2}{1.3}+\frac{2}{3.5}+\frac{2}{5.7}+\frac{2}{7.9}+\frac{2}{9.11}\right).y=\frac{4}{3}\)
\(\Leftrightarrow\left(\frac{3-1}{1.3}+\frac{5-3}{3.5}+\frac{7-5}{5.7}+\frac{9-7}{7.9}+\frac{11-9}{9.11}\right).y=\frac{4}{3}\)
\(\Leftrightarrow\left(1-\frac{1}{3}+\frac{1}{3}-\frac{1}{5}+\frac{1}{5}-\frac{1}{7}+\frac{1}{7}-\frac{1}{9}+\frac{1}{9}-\frac{1}{11}\right).y=\frac{4}{3}\)
\(\Leftrightarrow\left(1-\frac{1}{11}\right).y=\frac{4}{3}\)
\(\Leftrightarrow\frac{10}{11}.y=\frac{4}{3}\)
\(\Leftrightarrow y=\frac{4}{3}:\frac{10}{11}=\frac{4}{3}.\frac{11}{10}=\frac{22}{15}\)
Chú ý dấu \(\left(.\right)\)là dấu \(\left(\times\right)\)
Vậy \(y=\frac{22}{15}\)
\(\left(\frac{1}{1.3}+\frac{1}{3.5}+\frac{1}{5.7}+\frac{1}{7.9}+\frac{1}{9.11}\right).y=\frac{2}{3}\)
\(\Leftrightarrow\frac{1}{2}.\left(1-\frac{1}{3}+\frac{1}{3}-\frac{1}{5}+\frac{1}{5}-\frac{1}{7}+\frac{1}{7}-\frac{1}{9}+\frac{1}{9}-\frac{1}{11}\right).y=\frac{2}{3}\)
\(\Leftrightarrow\frac{1}{2}.\left(1-\frac{1}{11}\right).y=\frac{2}{3}\)
\(\Leftrightarrow\frac{1}{2}.\frac{10}{11}.y=\frac{2}{3}\)
\(\Leftrightarrow\frac{5}{11}.y=\frac{2}{3}\)
\(\Rightarrow y=\frac{2}{3}:\frac{5}{11}=\frac{22}{15}\)
LƯU Ý:các dấu chấm(.) là dấu nhân ^^.
\(\frac{1}{2}\cdot\left(2x-\frac{7}{3}\right)+\frac{1}{2}\left(2x+\frac{7}{5}\right)=0\)
\(\frac{1}{2}\cdot\left(2x-\frac{7}{3}+2x+\frac{7}{5}\right)=0\)
\(4x-\frac{14}{15}=0\)
\(4x=\frac{14}{15}\)
\(x=\frac{7}{30}\)
\(x\times\frac{3}{5}-\frac{1}{2}=\frac{4}{5}\)
\(\Rightarrow x\times\frac{6}{10}-\frac{5}{10}=\frac{4}{5}\)
\(\Rightarrow x\times\frac{1}{10}=\frac{4}{5}\)
\(\Rightarrow x=\frac{4}{5}:\frac{1}{10}\)
\(\Rightarrow x=\frac{4}{5}\cdot\frac{10}{1}\)
\(\Rightarrow x=\frac{40}{5}=8\)
Vậy x = 8
\(\dfrac{1}{2}-\dfrac{1}{2}\left(3-2x\right)=0\)
\(\Rightarrow\dfrac{1}{2}\left[1-\left(3-2x\right)\right]=0\)
\(\Rightarrow\dfrac{1}{2}\left[1-3+2x\right]=0\)
\(\Rightarrow\dfrac{1}{2}\left[2x-2\right]=0\)
\(\Rightarrow2x-2=0\Rightarrow2x=2\Rightarrow x=1\)
x = 1 nha Nhật