Câu 1 : tính hợp lý a, -7/9.4/11+-7/9.7/11+5 7/9 b,-7/25.11/33+-7/25 .2/13-18/25

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1. $\text{Tính hợp lí:}$

   $\text{a) $\dfrac{-7}{9}$.$\dfrac{4}{11}$ + $\dfrac{-7}{9}$.$\dfrac{7}{11}$ + $5\dfrac{7}{9}$}$

   $\text{= $\dfrac{-7}{9}$.$(\dfrac{4}{11}$ + $\dfrac{7}{11})$ + $5\dfrac{7}{9}$}$

   $\text{= $\dfrac{-7}{9}$.$\dfrac{11}{11}$ + $5\dfrac{7}{9}$}$

   $\text{= $\dfrac{-7}{9}$.1 + $5\dfrac{7}{9}$}$

   $\text{= $\dfrac{-7}{9}$ + $5\dfrac{7}{9}$}$

   $\text{= $\dfrac{-7}{9}$ + $\dfrac{52}{9}$}$

   $\text{= $\dfrac{45}{9}$}$

   $\text{= 5.}$

   $\text{b) $\dfrac{-7}{25}$.$\dfrac{11}{33}$ + $\dfrac{-7}{25}$.$\dfrac{2}{13}$ – $\dfrac{18}{25}$}$

   $\text{= $\dfrac{-7}{25}$.$(\dfrac{11}{33}$ + $\dfrac{2}{13})$ – $\dfrac{18}{25}$}$

   $\text{= $\dfrac{-7}{25}$.$(\dfrac{1}{3}$ + $\dfrac{2}{13})$ – $\dfrac{18}{25}$}$

   $\text{= $\dfrac{-7}{25}$.$(\dfrac{13}{39}$ + $\dfrac{6}{39})$ – $\dfrac{18}{25}$}$

   $\text{= $\dfrac{-7}{25}$.$\dfrac{19}{39}$ – $\dfrac{18}{25}$}$

   $\text{= $\dfrac{-133}{975}$ – $\dfrac{18}{25}$}$

   $\text{= $\dfrac{-133}{975}$ – $\dfrac{702}{975}$}$

   $\text{= $\dfrac{-835}{975}$}$

   $\text{= $\dfrac{-167}{195}$.}$

   $\text{Cho anh xin câu trả lời hay nhất nha. Câu trả lời của anh đầy đủ}$

   $\text{và chi tiết hơn bạn kia.}$

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2. Đáp án:

   Giải thích các bước giải:

   Câu 1: Tính hợp lý

   a) -7/9 x 4/11 + -7/9 x 7/11 + 5 7/9

   = -7/9 x ( 4/11 + 7/11 ) + 35/9

   = -7/9 x 1 + 35/9

   = -7/9 + 35/9

   = 28/9

   b) -7/25 x 11/33 + -7/25 x 2/13 – 18/25

   = -7/25 x ( 11/33 + 2/13 ) – 18/25

   = -7/25 x 19/39 – 18/25

   = -133/975 – 18/25

   = -167/195

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