Bài 11: Tính chất cơ bản của phép nhân phân số

1) \(\dfrac{3}{8}-\dfrac{4}{5}-\dfrac{-17}{40}=\dfrac{15}{40}-\dfrac{32}{40}-\dfrac{-17}{40}=\dfrac{-17}{40}-\dfrac{-17}{40}=\dfrac{34}{40}=\dfrac{17}{20}\)

2) \(\dfrac{3}{4}-\dfrac{16}{32}+\dfrac{4}{-3}=\dfrac{3}{4}-\dfrac{1}{2}+\dfrac{-4}{3}=\dfrac{9}{12}-\dfrac{6}{12}+\dfrac{-16}{12}=\dfrac{-13}{12}\)

3) \(\dfrac{-4}{7}+\dfrac{2}{3}.\dfrac{-9}{14}=\dfrac{-4}{7}+\dfrac{-3}{7}=-1\)

4) \(8\dfrac{2}{7}-\left(3\dfrac{4}{9}+4\dfrac{2}{7}\right)=\dfrac{58}{7}-\left(\dfrac{31}{9}+\dfrac{30}{7}\right)=\dfrac{58}{7}-\dfrac{31}{9}-\dfrac{30}{7}=\dfrac{58}{7}-\dfrac{30}{7}-\dfrac{31}{9}=\dfrac{28}{7}-\dfrac{31}{9}=4-\dfrac{31}{9}=\dfrac{36}{9}-\dfrac{31}{9}=\dfrac{5}{9}\)

5)

\(\left(\dfrac{2}{3}-1\dfrac{1}{2}\right):\dfrac{4}{3}+\dfrac{1}{2}=\left(\dfrac{2}{3}-\dfrac{3}{2}\right):\dfrac{4}{3}+\dfrac{1}{2}=\left(\dfrac{4}{6}-\dfrac{9}{6}\right):\dfrac{4}{3}+\dfrac{1}{2}=\dfrac{-5}{6}:\dfrac{4}{3}+\dfrac{1}{2}=\dfrac{-5}{6}.\dfrac{3}{4}+\dfrac{1}{2}=\dfrac{-5}{8}+\dfrac{1}{2}=\dfrac{-5}{8}+\dfrac{4}{8}=\dfrac{-1}{8}\)

6, \(\dfrac{-5}{13}+\dfrac{2}{5}+\dfrac{-8}{13}+\dfrac{3}{5}-\dfrac{3}{7}=\left(\dfrac{-5}{13}+\dfrac{-8}{13}\right)+\left(\dfrac{2}{5}+\dfrac{3}{5}\right)=-1+1=0\)

Đây là câu 6

bạn đăng từng câu 1 đc ko

1) 3/8-3/4-(-17/40)

=-3/8-(17/40)

=1/20

2)3/4-16/32+4/-3

=3/4-16/32+-4/3

=1/4+(-4/3)

=-13/12

4) [8]2/7-([3]4/9+[4]2/7)

=58/7-(31/9+30/7)

=58/7-31/9-30/7

=(58/7-30/7)-31/9

=5/9

5)(2/3-[1]1/2):4/3+1/2

(2/3-3/2):4/3+1/2

=-5/6:4/3+1/2

=-5/8+1/2

=-1/8

6)-5/13+2/5+-8/13+3/5-3/7

=(-5/13+(-8/13))+(2/5+3/5)-3/7

=-1+1-3/7

=-3/7

96,3

1,66

Giúp vs ak 

96,3

1,66

-3/7 + (-9)/35 + 2/-5

= -38/35

-38/35

= -3/7 + -9/35 + 2/-5

= -38/35

\(=\left(-\dfrac{5}{9}-\dfrac{4}{9}\right)+\left(\dfrac{8}{15}+\dfrac{7}{15}\right)-\dfrac{2}{11}=-\dfrac{2}{11}\)

\(\dfrac{-5}{9}+\dfrac{8}{15}+\dfrac{-2}{11}+\dfrac{4}{-9}+\dfrac{7}{15}.\\ =\left(\dfrac{-5}{9}+\dfrac{-4}{9}\right)+\left(\dfrac{8}{15}+\dfrac{7}{15}\right)-\dfrac{2}{11}.\\ =-1+1-\dfrac{2}{11}.\\ =-\dfrac{2}{11}.\)

tk

Cho đoạn thẳng AB=10cm. Trên đoạn thẳng AB lấy điểm C sao cho AC=4cm. Gọi M và N lần lượt là trung điểm của các đoạn thẳ... - Hoc24

tham khảo :

⇔13540-5x=3885

⇔5x=9655

⇔x=1931

= 1931

=5400

\(1+\dfrac{1}{2}.\dfrac{3.2}{2}+\dfrac{1}{3}.\dfrac{4.3}{2}+...+\dfrac{1}{500}.\dfrac{501.500}{2}\)

\(=\dfrac{2}{2}+\dfrac{3}{2}+\dfrac{4}{2}+...+\dfrac{501}{2}\)

\(=\dfrac{2+3+4+...+501}{2}\)

\(=\dfrac{\left(501-2+1\right).\left(501+2\right)}{4}\)

\(=\dfrac{\left(501-2+1\right).\left(501+2\right)}{4}=62875\)

Ta có: \(5\dfrac{1}{5}< x\dfrac{4}{15}< 9\dfrac{4}{13}\)

\(\Leftrightarrow\dfrac{26}{5}< \dfrac{15x+4}{15}< \dfrac{131}{13}\)

\(\Leftrightarrow\dfrac{1014}{195}< \dfrac{13\left(15x+4\right)}{195}< \dfrac{1965}{195}\)

\(\Leftrightarrow1014< 195x+52< 1965\)

\(\Leftrightarrow\left\{{}\begin{matrix}195x>962\\195x< 2017\end{matrix}\right.\Leftrightarrow\dfrac{962}{195}< x< \dfrac{2017}{195}\)

\(\Leftrightarrow x\in\left\{5;6;7;8;9;10\right\}\)