\(\frac{1}{1-\frac{1}{1-\frac{1}{2}}}+\frac{1}{1+\frac{1}{1+\frac{1}{2}}}\)

\(=\frac{1}{1-\frac{1}{\frac{1}{2}}}+\frac{1}{1+\frac{1}{\frac{3}{2}}}\)

\(=\frac{1}{1-2}+\frac{1}{1+\frac{2}{3}}=-1+\frac{1}{\frac{5}{3}}\)

\(=-1+\frac{3}{5}=\frac{-2}{5}\)

\(\frac{1}{1-\frac{1}{1-\frac{1}{2}}}+\frac{1}{1+\frac{1}{1+\frac{1}{2}}} =\frac{1}{\frac{1-\frac{1}{2}-1}{1-\frac{1}{2}}}+\frac{1}{\frac{1+\frac{1}{2}+1}{1+\frac{1}{2}}}\)

\(=\frac{1-\frac{1}{2}}{\frac{-1}{2}}+\frac{1+\frac{1}{2}}{2+\frac{1}{2}}=\frac{\frac{2-1}{2}}{\frac{-1}{2}}+\frac{\frac{2+1}{2}}{\frac{4+1}{2}}\)

\(=\frac{\frac{3}{2}}{\frac{-1}{2}}+\frac{\frac{3}{2}}{\frac{5}{2}}=\frac{3}{2}.\frac{2}{-1}+\frac{3}{2}.\frac{2}{5}\)

\(=-3+\frac{3}{5}=\frac{-15+3}{5}=\frac{-12}{5}\)

49

sai thi thoi

2A=2+2²+2³+...+2²⁰⁰+2²⁰¹

2A-A=2+2²+2³+...+2²⁰⁰+2²⁰¹-1-2-2²-...2²⁰⁰

​A=1+2²⁰¹

vậy A=1+2²⁰¹

^{tk mk nha}

tên khác có đc hơm ???

rãnh quá nhể ?

ai trả lời nhanh mình k cho mình cần luôn

đề bài kiểu j vậy

C ở đâu

các bn giúp mk nhé ai nhanh nhất mk tk cho.

1) 

Tổng của \(\widehat{B}\) và \(\widehat{C}\) là:

\(180^o-60^o=120^o\)

Ta có \(\widehat{B}=2\widehat{C}\Leftrightarrow\widehat{B}=\frac{2}{1}\widehat{C}\)

Áp dụng bài toán tổng tỉ.

Tổng số phần bằng nhau là:

2 + 1 = 3 phần.

Góc B là:

120 : 3 x 2 = 80 độ

Góc C là:

120 - 80 = 40 độ.

Vậy ......................

2) Theo đề ta có:

\(\frac{\widehat{A}}{2}=\frac{\widehat{B}}{3}=\frac{\widehat{C}}{4}\)  và \(\widehat{A}+\widehat{B}+\widehat{C}=180^o\)

Áp dụng tính chất của dãy tỉ số bằng nhau:

\(\frac{\widehat{A}}{2}=\frac{\widehat{B}}{3}=\frac{\widehat{C}}{4}=\frac{\widehat{A}+\widehat{B}+\widehat{C}}{2+3+4}=\frac{180^o}{9}=20^o\)

\(\hept{\begin{cases}\frac{\widehat{A}}{2}=20^o\Rightarrow\widehat{A}=20^o.2=40^o\\\frac{\widehat{B}}{3}=20^o\Rightarrow\widehat{B}=20^o.3=60^o\\\frac{\widehat{C}}{4}=20^o\Rightarrow\widehat{C}=20^o.4=80^o\end{cases}}\)

Vậy ..............................

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