Câu hỏi của Phan Thanh Hà

Question

$\frac{1}{2}+\frac{1}{4}+\frac{1}{8}+\frac{1}{16}+\frac{1}{32}=\frac{1}{x}$

Uyên · Accepted Answer

$\frac{1}{2}+\frac{1}{4}+\frac{1}{8}+\frac{1}{16}+\frac{1}{32}$$=1-\frac{1}{2}+\frac{1}{2}-\frac{1}{4}+\frac{1}{4}-\frac{1}{8}+\frac{1}{8}-\frac{1}{16}+\frac{1}{16}-\frac{1}{32}$$=1-\frac{1}{32}$$=\frac{31}{32}$có tử = 1 thì k bt à nhaCâu trả lời: $\frac{1}{2}+\frac{1}{4}+\frac{1}{8}+\frac{1}{16}+\frac{1}{32}$$=1-\frac{1}{2}+\frac{1}{2}-\frac{1}{4}+\frac{1}{4}-\frac{1}{8}+\frac{1}{8}-\frac{1}{16}+\frac{1}{16}-\frac{1}{32}$$=1-\frac{1}{32}$$=\frac{31}{32}$có tử = 1 thì k bt à nha

Không Tên · Answer

Đặt:  $A=\frac{1}{2}+\frac{1}{4}+\frac{1}{8}+\frac{1}{16}+\frac{1}{32}$$\Rightarrow$$2A=1+\frac{1}{2}+\frac{1}{4}+\frac{1}{8}+\frac{1}{16}$$\Rightarrow$$2A-A=\left(1+\frac{1}{2}+\frac{1}{4}+\frac{1}{8}+\frac{1}{16}\right)-\left(\frac{1}{2}+\frac{1}{4}+\frac{1}{8}+\frac{1}{16}+\frac{1}{32}\right)$$\Rightarrow$$A=1-\frac{1}{32}=\frac{31}{32}$mà  $A=\frac{1}{x}$nên   $\frac{1}{x}=\frac{31}{32}$$\Rightarrow$$x=\frac{32}{31}$Vậy...Câu trả lời: Đặt:  $A=\frac{1}{2}+\frac{1}{4}+\frac{1}{8}+\frac{1}{16}+\frac{1}{32}$$\Rightarrow$$2A=1+\frac{1}{2}+\frac{1}{4}+\frac{1}{8}+\frac{1}{16}$$\Rightarrow$$2A-A=\left(1+\frac{1}{2}+\frac{1}{4}+\frac{1}{8}+\frac{1}{16}\right)-\left(\frac{1}{2}+\frac{1}{4}+\frac{1}{8}+\frac{1}{16}+\frac{1}{32}\right)$$\Rightarrow$$A=1-\frac{1}{32}=\frac{31}{32}$mà  $A=\frac{1}{x}$nên   $\frac{1}{x}=\frac{31}{32}$$\Rightarrow$$x=\frac{32}{31}$Vậy...

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