\(\frac{12}{2.5}+\frac{12}{5.8}+\frac{12}{8.11}+...+\frac{12}{29.32}\)
\(=4.\left(\frac{3}{2.5}+\frac{3}{5.8}+\frac{3}{8.11}+...+\frac{3}{29.32}\right)\)
\(=4.\left(\frac{1}{2}-\frac{1}{5}+\frac{1}{5}-\frac{1}{8}+\frac{1}{8}-\frac{1}{11}+...+\frac{1}{29}-\frac{1}{32}\right)\)
\(=4.\left(\frac{1}{2}-\frac{1}{32}\right)\)
\(=4.\frac{15}{32}\)
\(=\frac{15}{8}\)
_Chúc bạn học tốt_
\(\frac{12}{2.5}+\frac{12}{5.8}+\frac{12}{8.11}+....+\frac{12}{29.32}\)
\(=4\left(\frac{3}{2.5}+\frac{3}{5.8}+\frac{3}{8.11}+...+\frac{3}{29.32}\right)\)
\(=4\left(\frac{1}{2}-\frac{1}{5}+\frac{1}{5}-\frac{1}{8}+...+\frac{1}{29}-\frac{1}{32}\right)\)
\(=4\left(\frac{1}{2}-\frac{1}{32}\right)\)
\(=4.\frac{15}{32}=\frac{15}{8}\)
Đặt A= 12/2*5+12/5*8+12/8*11+....+12/29*32
A= 4*(3/2*5+3/5*8+3/8*11+...+3/29*32)
A = 4*(1/2-1/5+1/5-1/8+1/8-1/11+....+1/29-1/32)
A= 4*(1/2-1/32)
A= 4*15/32
A= 15/8
