TRẢ LỜI :
`A=` $\frac{1}{2.4}$ `+` $\frac{1}{4.6}$ `+...` $\frac{1}{48.50}$
`A=` $\frac{1}{2}$ . ($\frac{2}{2.4}$ `+` $\frac{2}{4.6}$ `+...`$\frac{2}{48.50}$ )
`A=` $\frac{1}{2}$ `.`($\frac{1}{2}$`-`$\frac{1}{4}$ `+` $\frac{1}{4}$ `-` $\frac{1}{6}$ `+...+` $\frac{1}{48}$`-`$\frac{1}{50}$ )
`A=`$\frac{1}{2}$ `.`($\frac{1}{2}$`-`$\frac{1}{50}$ )
`A=` $\frac{1}{2}$ `.` $\frac{12}{25}$
`A=` $\frac{6}{25}$
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Học tốt ^^
Xin hay nhất ><
