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1$\dfrac{1}{12}x1\dfrac{1}{13}x1\dfrac{1}{14}$ x ... x $1\dfrac{1}{2005}$

Nguyễn Thị Thương Hoài · Accepted Answer

1$\dfrac{1}{12}$ $\times$ 1$\dfrac{1}{13}$ $\times$ 1$\dfrac{1}{14}$ $\times$...$\times$1$\dfrac{1}{2005}$

A = $\dfrac{12+1}{12}$ $\times$ $\dfrac{13+1}{13}$ $\times$ $\dfrac{14+1}{14}$$\times$...$\times$ $\dfrac{2006}{2005}$

A = $\dfrac{13}{12}$ $\times$ $\dfrac{14}{13}$ $\times$ $\dfrac{15}{14}$ $\times$...$\times$ $\dfrac{2006}{2005}$

A = $\dfrac{2006}{12}$

A = $\dfrac{1003}{6}$Câu trả lời:       1$\dfrac{1}{12}$ $\times$ 1$\dfrac{1}{13}$ $\times$ 1$\dfrac{1}{14}$ $\times$...$\times$1$\dfrac{1}{2005}$

A = $\dfrac{12+1}{12}$ $\times$ $\dfrac{13+1}{13}$ $\times$ $\dfrac{14+1}{14}$$\times$...$\times$ $\dfrac{2006}{2005}$

A = $\dfrac{13}{12}$ $\times$ $\dfrac{14}{13}$ $\times$ $\dfrac{15}{14}$ $\times$...$\times$ $\dfrac{2006}{2005}$

A = $\dfrac{2006}{12}$

A = $\dfrac{1003}{6}$