đề bài là j bạn?? 

so sánh à bạn 

là tính tổng á

A= ( 6 - 2/3 + 1/2) -( 5 +5/3 - 3/2) - (3 - 1/3 + 5/2)

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

= (6-5-3) - (2/3 + 5/2 - 1/3) + (1/2 +3/2 -5/2)

= -2 - 2 + (-1/2)

= -4 -1/2

=-9/2

A = ( 6 - 1 ) - ( 5 + 1 / 6 ) - ( 3 + 13 / 6 )

A = 5 - 31 / 6 - 31 / 6

A = -16 / 3

Ta có: \(A=\dfrac{1-0.5\cdot\left(3.84-2.4\right):0.8}{\dfrac{4}{5}-\left(1\dfrac{1}{3}-2\dfrac{1}{6}\right)-1.5}\)

\(=\dfrac{1-0.5\cdot1.44:0.8}{\dfrac{4}{5}-\left(\dfrac{4}{3}-\dfrac{13}{6}\right)-\dfrac{3}{2}}\)

\(=\dfrac{1-0.9}{\dfrac{4}{5}+\dfrac{5}{6}-\dfrac{3}{2}}=\dfrac{0.1}{\dfrac{2}{15}}=\dfrac{3}{4}\)

Giải:

A=1-0,5.(3,84-2,4):0,8 / 4/5-(1 1/3 - 2 1/6)-1,5

A=1-0,5.1,44:0.8 / 4/5-(4/3-13/6)-3/2

A=1-0.9 / 4/5-(-5/6)-3/2

A=0.1 / 2/15

A= 1/10 : 2/15

A=3/4

Chúc bạn học tốt!

c)

\(\left(1-\frac{1}{2}\right)+\left(1-\frac{1}{6}\right)+....+\left(1-\frac{1}{42}\right)+\left(1-\frac{1}{56}\right)\)

\(\left(1+1+1+....+1+1\right)+\left(\frac{1}{1\times2}+\frac{1}{2\times3}+...+\frac{1}{6\times7}+\frac{1}{7\times8}\right)\)(Có  7 số 1)

\(7+1-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+....+\frac{1}{6}-\frac{1}{7}+\frac{1}{7}-\frac{1}{8}\)

\(7+1-\frac{1}{8}=\frac{63}{8}\)

Gợi ý 1 bài c) còn d) e) cũng làm như vậy nhé

Chúc bạn học tốt !!!

Câu a:

x - 1: 4/3 + 9/16 = - 5^2/4^2

x - 1 x 3/4 + 9/16 = - 25/16

x - 3/4 + 9/16 = - 25/16

x - 3/4 = -25/16 - 9/16

x - 3/4 = -17/8

x = - 17/8 + 3/4

x = -11/8

Vậy x = -11/8

Câu b:

5/2x + 2 - 3 1/2 = 1/6

5/2x + 2 - 7/2 = 1/6

5/2x = 1/6 + 7/2 - 2

5/2x = 1/6 + 21/6 - 12/6

5/2x = 5/3

x = 5/3 : 5/2

x = 2/3

Câu a:

7/10.4/9 + 3/10.4/9 - 1 7/9

= 4/9.(7/10 + 3/10) - 16/9

= 4/9 - 16/9

= - 12/9

= - 4/3

Câu b:

- 5/6 + 4/9.(5/4 - 2/3).(-3)^2 + 5/9.30%

= - 5/6 + [5/9 - 8/27].9 + 5/9.3/10

= - 5/6 + 5 - 8/3 + 1/6

= (-5/6 + 1/6) - 8/3 + 5

= - 4/6 - 8/3 + 15/3

= - 2/3 - 8/3 + 15/3

= - 10/3 + 15/3

= 5/3