Question

3.x/2.5+3.x/5.8+3.x/8.11+3.x/11.4=1/21

Answer 1

mạo phép chỉnh đề:

\(\frac{3x}{2.5}+\frac{3x}{5.8}+\frac{3x}{8.11}+\frac{3x}{11.14}=\frac{1}{21}\)

<=>  \(x\left(\frac{3}{2.5}+\frac{3}{5.8}+\frac{3}{8.11}+\frac{3}{11.14}\right)=\frac{1}{21}\)

<=>  \(x\left(\frac{1}{2}-\frac{1}{5}+\frac{1}{5}-\frac{1}{8}+\frac{1}{8}-\frac{1}{11}+\frac{1}{11}-\frac{1}{14}\right)=\frac{1}{21}\)

<=>  \(x\left(\frac{1}{2}-\frac{1}{14}\right)=\frac{1}{21}\)

<=>  \(x.\frac{3}{7}=\frac{1}{21}\)

<=>  \(x=\frac{1}{9}\)

Vậy...