7 x 3 = 21 6 x 4 = 24 5 x 6 = 30 6 x 7 = 42

49  : 7 =  7       36 : 6 = 6        28 : 7 = 4         48 : 6 = 8

Học sinh nhẩm và ghi kết quả như sau:

6 x 9 = 54

28 : 7 = 4

7 x 7 = 49

56 : 7 = 8

7 x 8 = 56

36 : 6 = 6

6 x 3 = 18

48 : 6 = 8

6 x 5 = 30

42 : 7 = 6

7 x 5 = 35

40 : 5 = 8

6 x 9 = 54

28 : 7 = 4

7 x 7 = 49

a) Ta có: \(\dfrac{7}{36}-\dfrac{8}{-9}+\dfrac{-2}{3}\)

\(=\dfrac{7}{36}+\dfrac{32}{36}+\dfrac{-24}{36}\)

\(=\dfrac{15}{36}=\dfrac{5}{12}\)

b) Ta có: \(\dfrac{-3}{8}\cdot\dfrac{1}{6}+\dfrac{-3}{8}\cdot\dfrac{5}{6}+\dfrac{-10}{16}\)

\(=\dfrac{-3}{8}+\dfrac{-10}{16}\)

\(=\dfrac{-6+\left(-10\right)}{16}=\dfrac{-16}{16}=-1\)

2/7

11/21

2/7

11/21

S=7(1+1/3+1/6+...+1/55)

=7(2/2+2/6+...+2/110)

=14(1/2+1/6+...+1/110)

=14(1-1/2+1/2-1/3+...+1/10-11)

=14*10/11=140/11

CẢM ƠN

a)\(\frac{6}{14}-\left(\frac{-18}{36}\right)-\frac{5}{15}=\frac{3}{7}+\frac{1}{2}-\frac{1}{3}=\frac{25}{42}\)

b) \(\frac{-36}{45}-\frac{25}{10}-\frac{22}{33}=\frac{-4}{5}-\frac{5}{2}-\frac{2}{3}=\frac{-119}{30}\)

c) \(\frac{-10}{3}+\frac{13}{10}-\frac{1}{6}+\frac{7}{70}=\frac{-10}{3}+\frac{13}{10}-\frac{1}{6}+\frac{1}{7}=\frac{-72}{35}\)

CHÚC BN HỌC TỐT!!
 

j toanf dua manh nayfyhi ko tr loi duoc

a: 6^9=(6^3)^3=216^3>15^3

B: 6^36=(6^2)^18=36^18>35^18

c: 7^18=(7^2)^9=49^9>30^9

d: 3^500=243^100

7^300=343^100

=>3^500<7^300

\(a)\dfrac{3}{4}-\dfrac{2}{7}=\dfrac{21-8}{28}=\dfrac{13}{28}.\\ b)\dfrac{3}{8}-\dfrac{5}{16}=\dfrac{6-5}{16}=\dfrac{1}{16}.\)

\(c)\dfrac{7}{5}-\dfrac{2}{3}=\dfrac{21-10}{15}=\dfrac{11}{15}.\\ d)\dfrac{31}{36}-\dfrac{5}{6}=\dfrac{31-30}{36}=\dfrac{1}{36}.\)