-207/221

đây chỉ là kết quả thôi cách làm mình sẽ đăng sau

bạn đăng nhanh lên nhé . mình đang cần lắm

thôi cách làm để mình nghĩ . mình tích luôn cho bạn rồi đấy

Ta có: \(A=\dfrac{5}{13}+\dfrac{-5}{7}+\dfrac{-20}{41}+\dfrac{8}{13}+\dfrac{-21}{41}\)

\(=\left(\dfrac{5}{13}+\dfrac{8}{13}\right)+\left(\dfrac{-20}{41}+\dfrac{-21}{41}\right)+\dfrac{-5}{7}\)

\(=1-1+\dfrac{-5}{7}\)

\(=\dfrac{-5}{7}\)

Có 2 dấu = hả bạn

\(A=\dfrac{5}{13}+\dfrac{-5}{7}+\dfrac{-20}{41}+\dfrac{8}{13}+\dfrac{-21}{41}=(\dfrac{5}{13}+\dfrac{8}{13})+(\dfrac{-20}{41}+\dfrac{-21}{41})+(\dfrac{-5}{7})=1+\left(-1\right)+\dfrac{-5}{7}=0+\dfrac{-5}{7}=\dfrac{-5}{7}\)

\(\dfrac{5}{13}+\dfrac{5}{17}+\dfrac{-20}{41}+\dfrac{8}{13}+\dfrac{-21}{41}\)

\(=\left(\dfrac{5}{13}+\dfrac{8}{13}\right)+\left(\dfrac{-20}{41}+\dfrac{-21}{41}\right)+\dfrac{5}{17}\)

\(=1+\left(-1\right)+\dfrac{5}{17}\)

\(=0+\dfrac{5}{17}=\dfrac{5}{7}\)

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\(=\left(\dfrac{5}{13}+\dfrac{8}{13}\right)+\left(\dfrac{-20}{41}+\dfrac{-21}{41}\right)+\dfrac{5}{17}\)

\(=1+\left(-1\right)+\dfrac{5}{17}\)

\(=0+\dfrac{5}{17}\)

\(=\dfrac{5}{17}\)

\(\dfrac{5}{13}+\dfrac{5}{17}+\dfrac{-20}{41}+\dfrac{8}{13}+\dfrac{-21}{41}\)

= \(\left(\dfrac{5}{13}+\dfrac{8}{13}\right)+\left(\dfrac{-20}{41}+\dfrac{-21}{41}\right)+\dfrac{5}{17}\)

= \(1+\left(-1\right)+\dfrac{5}{17}\)

= \(0+\dfrac{5}{17}\)

= \(\dfrac{5}{17}\)

\(\frac{5}{13}+-\frac{5}{17}+-\frac{20}{41}+\frac{8}{13}+-\frac{21}{41}\)

\(=\left(\frac{5}{13}+\frac{8}{13}\right)+\left(-\frac{20}{41}+-\frac{21}{41}\right)+-\frac{5}{17}\)

\(=1+\left(-1\right)+-\frac{5}{17}\)

\(=0+-\frac{5}{17}\)\(=-\frac{5}{17}\)

Ủng hộ tk Đúng nhé mọi người !!! ^^ 

\(\frac{5}{13}+\left(-\frac{5}{7}\right)+\left(-\frac{20}{41}\right)+\frac{8}{13}+\left(-\frac{21}{41}\right)\)

\(=\left(\frac{5}{13}+\frac{8}{13}\right)+\left(-\frac{20}{41}+\frac{-21}{41}\right)+\left(-\frac{5}{7}\right)\)

\(=1+\left(-1\right)+\left(-\frac{5}{7}\right)\)

\(=0+\left(-\frac{5}{7}\right)=-\frac{5}{7}\)

\(\left(\frac{5}{13}+\frac{8}{13}\right)+\left(\frac{-20}{41}+\frac{-21}{41}\right)+\frac{-5}{7}\)

\(=1+\left(-1\right)+\frac{-5}{7}\)

\(=\left(1-1\right)+\frac{-5}{7}\)

\(=0+\frac{-5}{7}\)

\(=\frac{-5}{7}\)

1: =5/13+8/13-20/41-21/41-5/17

=1-1-5/17=-5/17

2: =1/5+4/5-2/9-7/9+16/17

=16/17+1-1=16/17

3: =1/3-1/5+1/5-1/7+...+1/99-1/101

=1/3-1/101

=98/303

\(\dfrac{5}{13}+\left(-\dfrac{5}{7}\right)+\left(-\dfrac{20}{41}\right)+\dfrac{8}{13}+\left(-\dfrac{21}{41}\right)\)

\(=\dfrac{5}{13}-\dfrac{5}{7}-\dfrac{20}{41}+\dfrac{8}{13}-\dfrac{21}{41}\)

\(=\left(\dfrac{5}{13}+\dfrac{8}{13}\right)-\left(\dfrac{20}{41}+\dfrac{21}{41}\right)-\dfrac{5}{7}\)

\(=\dfrac{13}{13}-\dfrac{41}{41}-\dfrac{5}{7}\)

\(=1-1-\dfrac{5}{7}\)

\(=0+\dfrac{5}{7}\)

\(=\dfrac{5}{7}\)

\(\dfrac{5}{13}+\dfrac{-5}{7}+\dfrac{-20}{41}+\dfrac{8}{13}+\dfrac{-21}{41}\)

\(=\left(\dfrac{5}{13}+\dfrac{8}{13}\right)+\left(\dfrac{-20}{41}+\dfrac{-21}{41}\right)+\dfrac{-5}{7}\)

\(=1+\left(-1\right)+\dfrac{-5}{7}\)

\(=\dfrac{-5}{7}\)

\(#PaooNqoccc\)

Bài làm :

-0.71428571428

Trả lời :

5/13 + - 5/7 + - 20/41 + 8/13 - 21/41 = -0.71428571428

~ Học tốt ~