Câu hỏi của Vũ Ngọc Trâm

Question

D=3/2*6+3/6*10+3/10*14+...+3/26*30

Xyz OLM · Accepted Answer

$D=\frac{3}{2.6}+\frac{3}{6.10}+\frac{3}{10.14}+..+\frac{3}{26.30}$$=\frac{3}{4}.\left(\frac{4}{2.6}+\frac{4}{6.10}+\frac{4}{10.14}+...+\frac{4}{26.30}\right)$$=\frac{3}{4}\left(\frac{1}{2}-\frac{1}{6}+\frac{1}{6}-\frac{1}{10}+\frac{1}{10}-\frac{1}{14}+...+\frac{1}{26}-\frac{1}{30}\right)$$=\frac{3}{4}\left(\frac{1}{2}-\frac{1}{30}\right)=\frac{3}{4}.\frac{7}{15}=\frac{7}{20}$Câu trả lời: $D=\frac{3}{2.6}+\frac{3}{6.10}+\frac{3}{10.14}+..+\frac{3}{26.30}$$=\frac{3}{4}.\left(\frac{4}{2.6}+\frac{4}{6.10}+\frac{4}{10.14}+...+\frac{4}{26.30}\right)$$=\frac{3}{4}\left(\frac{1}{2}-\frac{1}{6}+\frac{1}{6}-\frac{1}{10}+\frac{1}{10}-\frac{1}{14}+...+\frac{1}{26}-\frac{1}{30}\right)$$=\frac{3}{4}\left(\frac{1}{2}-\frac{1}{30}\right)=\frac{3}{4}.\frac{7}{15}=\frac{7}{20}$

Dương No Pro · Answer

$D=\frac{3}{2.6}+\frac{3}{6.10}+..+\frac{3}{26.30}$$D=3\left(\frac{1}{2.6}+\frac{1}{6.10}+..+\frac{1}{26.30}\right)$$4D=4.3.\left(\frac{1}{2.6}+\frac{1}{6.10}+..+\frac{1}{26.30}\right)$$4D=3\left(\frac{4}{2.6}+\frac{4}{6.10}+..+\frac{4}{26.30}\right)$$4D=3\left(\frac{1}{2}-\frac{1}{6}+\frac{1}{6}-\frac{1}{10}+..+\frac{1}{26}-\frac{1}{30}\right)$$4D=3\left(\frac{1}{2}-\frac{1}{30}\right)$$4D=3.\frac{7}{15}$$4D=\frac{7}{5}$$D=\frac{7}{5}:4=\frac{7}{20}$$\text{Vậy D =}\frac{7}{20}$Câu trả lời: $D=\frac{3}{2.6}+\frac{3}{6.10}+..+\frac{3}{26.30}$$D=3\left(\frac{1}{2.6}+\frac{1}{6.10}+..+\frac{1}{26.30}\right)$$4D=4.3.\left(\frac{1}{2.6}+\frac{1}{6.10}+..+\frac{1}{26.30}\right)$$4D=3\left(\frac{4}{2.6}+\frac{4}{6.10}+..+\frac{4}{26.30}\right)$$4D=3\left(\frac{1}{2}-\frac{1}{6}+\frac{1}{6}-\frac{1}{10}+..+\frac{1}{26}-\frac{1}{30}\right)$$4D=3\left(\frac{1}{2}-\frac{1}{30}\right)$$4D=3.\frac{7}{15}$$4D=\frac{7}{5}$$D=\frac{7}{5}:4=\frac{7}{20}$$\text{Vậy D =}\frac{7}{20}$

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