Lời giải:

$\frac{6}{4}\times \frac{19}{10}-\frac{3}{4}\times \frac{7}{10}+\frac{3}{4}:\frac{10}{69}$

$=\frac{6}{4}\times \frac{19}{10}-\frac{3}{4}\times \frac{7}{10}+\frac{3}{4}\times \frac{69}{10}$

$=\frac{6}{4}\times \frac{19}{10}+\frac{3}{4}\times (\frac{69}{10}-\frac{7}{10})$

$=\frac{3}{2}\times \frac{19}{10}+\frac{3}{4}\times \frac{62}{10}$

$=\frac{3}{2}\times \frac{19}{10}+\frac{3}{2}\times \frac{31}{10}$
$=\frac{3}{2}\times (\frac{19}{10}+\frac{31}{10})$

$=\frac{3}{2}\times \frac{50}{10}=\frac{3}{2}\times 5=\frac{15}{2}$

ai cũng giống chắc đúng rồi, nhưng giải ra cho mình đi

Kết quả = 

\(\frac{6}{4}\cdot\frac{19}{10}-\frac{3}{4}\cdot\frac{7}{10}+\frac{3}{4}:\frac{10}{69}=2^{ }_{ }\)\(\frac{15}{46}\)

vế 1   (6:4 =1.5 )x(19:10 =1.9)1,5x1,9 =2,85
vế 2   (3/4=0,75)x(7:10=0,7)0,75x0,7=0,525
vế 3   (3:4=0,75):(10:69=0,14492753623 lấy 3 chữ số ở hàng thập phân =0,144) 0,75:0,144=6,57894736842 lấy 3 chữ số ở hàng thập phân =6,578 
2,85 -0,525+6,578
=2,325+6,578
=8.903
(hơi rườm rà nếu có sai thông cảm)

vế 1   6/4 x 19/10=57/20
vế 2   3/4 x 7/10=21/40
vế 3   3/4 : 10/69 =207/40 
57/20 - 21/40 + 207/40
= 93/40 + 207/40
=15/2

a: \(\dfrac{5}{3}\cdot\dfrac{7}{10}=\dfrac{5}{10}\cdot\dfrac{7}{3}=\dfrac{14}{3}>2\)

\(\dfrac{5}{7}:\dfrac{7}{10}=\dfrac{5}{7}\cdot\dfrac{10}{7}=\dfrac{50}{49}< 2\)

=>\(\dfrac{5}{3}\cdot\dfrac{7}{10}>\dfrac{5}{7}:\dfrac{7}{10}\)

b: \(\dfrac{4}{5}\cdot\dfrac{5}{6}=\dfrac{4}{6}=\dfrac{2}{3}\)

\(\dfrac{8}{9}:\dfrac{4}{3}=\dfrac{8}{9}\cdot\dfrac{3}{4}=\dfrac{8}{4}\cdot\dfrac{3}{9}=\dfrac{2}{3}\)

Do đó: \(\dfrac{4}{5}\cdot\dfrac{5}{6}=\dfrac{8}{9}:\dfrac{4}{3}\)

c: \(\dfrac{5}{11}\cdot\dfrac{33}{15}=\dfrac{5}{15}\cdot\dfrac{33}{11}=\dfrac{3}{3}=1\)

\(\dfrac{6}{17}\cdot\dfrac{34}{25}=\dfrac{34}{17}\cdot\dfrac{6}{25}=2\cdot\dfrac{6}{25}=\dfrac{12}{25}< 1\)

=>\(\dfrac{5}{11}\cdot\dfrac{33}{15}>\dfrac{6}{17}\cdot\dfrac{34}{25}\)

d: \(\dfrac{15}{19}\cdot\dfrac{38}{5}=\dfrac{15}{5}\cdot\dfrac{38}{19}=3\cdot2=6\)

\(\dfrac{15}{16}:\dfrac{3}{8}=\dfrac{15}{16}\cdot\dfrac{8}{3}=\dfrac{15}{3}\cdot\dfrac{8}{16}=\dfrac{5}{2}\)<6

=>\(\dfrac{15}{19}\cdot\dfrac{38}{5}>\dfrac{15}{16}:\dfrac{3}{8}\)

tra loi nhanh ho mk voi

\(A=\frac{1}{2}+\frac{1}{6}+\frac{1}{12}+\frac{1}{20}+\frac{1}{30}+\frac{1}{42}\)

    = \(\frac{1}{1.2}+\frac{1}{2.3}+\frac{1}{3.4}+\frac{1}{4.5}+\frac{1}{5.6}+\frac{1}{6.7}\)

      = \(1-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+\frac{1}{4}-\frac{1}{5}+\frac{1}{5}-\frac{1}{6}+\frac{1}{6}-\frac{1}{7}\)

      = \(1-\frac{1}{7}\)

      =   \(\frac{7}{7}-\frac{1}{7}\)

        = \(\frac{6}{7}\)

2) \(\frac{7}{4}-x.\frac{4}{3}=\frac{5}{19}\)

              \(x.\frac{4}{3}=\frac{7}{4}-\frac{5}{19}\)

         \(x.\frac{4}{3}=\frac{133}{76}-\frac{20}{76}\)

\(x.\frac{4}{3}=\frac{113}{76}\)

      \(x=\frac{113}{76}:\frac{4}{3}\)

      \(x=\frac{399}{304}\)

VẬY \(x=\frac{399}{304}\)

b) \(\left(x+\frac{3}{4}\right).\frac{5}{7}=\frac{10}{9}\)

      \(\left(x+\frac{3}{4}\right)=\frac{10}{9}:\frac{5}{7}\)

     \(x+\frac{3}{4}=\frac{14}{9}\)

              \(x=\frac{14}{9}-\frac{3}{4}\)

               \(x=\frac{29}{36}\)

Vậy \(x=\frac{29}{36}\)

c) \(x.\frac{1}{2}+\frac{3}{2}.x=\frac{4}{5}\)

\(x.\left(\frac{1}{2}+\frac{3}{2}\right)=\frac{4}{5}\)

\(x.2=\frac{4}{5}\)

     \(x=\frac{4}{5}:2\)

      \(x=\frac{2}{5}\)

Vậy \(x=\frac{2}{5}\)

Chúc bạn học tốt !!!

Tính nhanh mỗi biểu thức sau:

a, 0 + 1 + 2 + 3 + 4 + 5 + 6 + 7 + 8 + 9 + 10 + 11 + 12 + 13 + 14 + 15 + 16 + 17 + 18 + 19 + 20

= (0 + 20) + (1 + 19) + (2 + 18) + (3 + 17) + (4 + 16) + (5 + 15) + (6 + 14) + (7 + 13) + (8 + 12) + (9 + 11) + 10

= 20 + 20 + 20 + 20 + 20 + 20 + 20 + 20 + 20 + 20 + 10

= 20 x 10 + 10

= 200 + 10

= 210

b, 1 x 2 x 3 x 4 x 5 x 6 x 7 x 8 x 9 x (4 x 9 - 36)

= 1 x 2 x 3 x 4 x 5 x 6 x 7 x 8 x 9 x (36 - 36)

= 1 x 2 x 3 x 4 x 5 x 6 x 7 x 8 x 9 x 0

= A x 0

= 0

c, (81 - 7 x 9 - 18) : (1 + 2 + 3 + 4 + 5 + 6 + 7 + 8 + 9)

= (81 - 63 - 18) : (1 + 2 + 3 + 4 + 5 + 6 + 7 + 8 + 9)

= (18 - 18) : (1 + 2 + 3 + 4 + 5 + 6 + 7 + 8 + 9)

= 0 :(1 + 2 + 3 + 4 + 5 + 6 + 7 + 8 + 9)

= 0 : A

= 0

d, (6 x 5 + 7 - 37) x (1 + 2 + 3 + 4 + 5 + 6 + 7 + 8 + 9 + 10)

= (30 + 7 - 37)  x (1 + 2 + 3 + 4 + 5 + 6 + 7 + 8 + 9 + 10)

= (37 - 37)  x (1 + 2 + 3 + 4 + 5 + 6 + 7 + 8 + 9 + 10)

= 0  x (1 + 2 + 3 + 4 + 5 + 6 + 7 + 8 + 9 + 10)

= 0 x A

= 0

e, (11 x 9 - 100 + 1) : (1 x 2 x 3 x 4 x ... x 10)

= (99 - 100 + 1) : (1 x 2 x 3 x 4 x ... x 10)

= (99 + 1 - 100) : (1 x 2 x 3 x 4 x ... x 10)

= (100 - 100) : (1 x 2 x 3 x 4 x ... x 10)

= 0 : (1 x 2 x 3 x 4 x ... x 10)

= 0 : A

= 0

g, (m : 1 - m x 1) : (m x 2008 + m x 2008)

= (m - m) : (m x 2008 + m x 2008)

= 0 : (m x 2008 + m x 2008)

= 0 : A

= 0

h, (2 + 4 + 6 + 8 + m x n) x (324 x 3 - 972)

= (2 + 4 + 6 + 8 + m x n) x (972 - 972)

= (2 + 4 + 6 + 8 + m x n) x 0

= A x 0

= 0

l, (1 + 2 + 3 + ... + 99)  x (13 x 15 - 12 x 15 - 15)

= (1 + 2 + 3 + ... + 99) x (15 x (13 - 12 - 1))

= (1 + 2 + 3 + ... + 99) x (15 x 0)

= (1 + 2 + 3 + ... + 99) x 0

= A x 0

= 0

i, (0 x 1 x 2 x...x 99 x 100) : (2 + 4 + 6 +...+ 98)

= 0 x : (2 + 4 + 6 +...+ 98)

= 0 x A

= 0

k, (0 + 1 + 2 +...+ 97 + 99) x (45 x 3 - 45 x 2 - 45)

= (0 + 1 + 2 +...+ 97 + 99) x (45 x (3 - 2 - 4))

= (0 + 1 + 2 +...+ 97 + 99) x (45 x 0)

= (0 + 1 + 2 +...+ 97 + 99) x 0

= A x 0

= 0

GIÚP MÌNH VỚI  

(-7) NHÂN (-24) + (-36) : (-3)^2 - (-5)^3

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