1. C = \(\frac{83}{41}\)
2. D = \(\frac{-79}{90}\)

a)

1/12 + 1/6 + 1/2 = (1+2+6)/12 = 9/12 = 3/4 
1/30 + 1/20 = (2+3)/60 = 5/60 = 1/12 
1/56 + 1/42 = 1/7(1/8+1/6) = 1/7 .(3+4)/24 = 1/24 
8/9- 1/72 = (8.8 - 1)/72 = 63/72 = 7/8 
1/12 + 1/24 = (2+1)/24 = 1/8 
7/8 - 1/8 = 6/8 = 3/4 
3/4 - 3/4 = 0 
 

b)

\(0,5+\frac{1}{3}+0,4+\frac{5}{7}+\frac{1}{6}-\frac{4}{35}\)

\(=\left(\frac{1}{2}+\frac{1}{3}+\frac{2}{3}+\frac{1}{6}\right)+\left(\frac{5}{7}-\frac{4}{35}\right)\)

\(=\frac{15+10+12+5}{30}+\frac{25-4}{35}\)

\(=\frac{7}{5}+\frac{3}{5}\)

\(=2\)

C=0.5+1/3+0.4+5/7+1/6-4/35+1/41

C=1/2+1/3+2/5+5/7+1/6-4/35+1/41

C=(1/2+1/6+1/3)+(2/5+5/7-4/35)+1/41

C=1+1-1/41

C=2-1/41

=>C=81/41

D=1/90-1/72-1/56-1/42-1/30-1/20--1/12-1/6-1/2

=> D=1/9*10-1/8*9-1/7*8-1/6*7-1/5*6-1/4*5-1/3*4-1/2*3-1/1*2

=>D=-(1/1-1/2+1/2-1/3+1/3-1/4+1/4-1/5+1/5-1/6+1/6-1/7+1/7-1/8+1/8-1/9+1/9-1/10)
=>D=-(1-1/10)

=>D=-9/10

ai k mh mh k lại

C.D=18/10 nha

`@` `\text {Ans}`

`\downarrow`

`1)`

`5/7*37 13/23 - 51 13/23*5/7`

`= 5/7* (37 13/23 - 51 13/23)`

`= 5/7* (-14)`

`= -10`

`2)`

`-2/3 +1/3+0,5+2 1/2`

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

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

`= -1/3 + 3`

`=8/3`

`3)`

`-0,5+2/3+1/2`

`= -1/2 + 2/3 + 1/2`

`= (-1/2 + 1/2) + 2/3`

`= 2/3`

`4)`

`(8+2 1/3-3/5) -(5+0,4)-(3 1/2 -2)`

`= 8+ 7/3 - 3/5 - 5 - 0,4 - 7/2 + 2`

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

`= 5 - 1 - 7/6`

`= 4 - 7/6 = 17/6`

`5)`

`(2/9-7/12):3/4+(16/9-5/12):3/4`

`= (2/9 - 7/12) \times 4/3 + (16/9 - 5/12) \times 4/3`

`= 4/3 *(2/9 - 7/12 + 16/9 - 5/12)`

`= 4/3 * [(2/9 + 16/9) + (-7/12 - 5/12)]`

`= 4/3 * ( 2 - 1)`

`= 4/3 * 1 = 4/3`

`6)`

`-(2021.0,7+19,75) +0,7- (8-19,75)`

`= -2021*0,7 -19,75 + 0,7 - 8 + 19,75`

`= 0,7*(-2021 + 1) - 8`

`= -1414-8`

`= -1422`

`7)`

`15/34+7/21+19/34-20/15`

`= (15/34 + 19/34) + 7/21 - 20/15`

`= 1 + 7/21 - 20/15`

`= 4/3 - 20/15 =0`

`8)`

`2 5/6+1/6:(-5/8)`

`= 17/6 + (-4/15)`

`= 77/30`

`9)`

`(-2)^2 +2/9. (4/5-2/3)`

`= 4 + 2/9*2/15`

`= 4+4/135`

`= 544/135`

`10)`

`(-1/5+3/7):5/4+(-4/5+4/7):5/4`

`= (-1/5+3/7) * 4/5 + (-4/5+4/7) * 4/5`

`= 4/5*(-1/5 +3/7-4/5+4/7)`

`= 4/5*[(-1/5-4/5)+(3/7+4/7)]`

`= 4/5* (-1+1)`

`= 4/5*0=0`

`11)`

`2022,2021 . 1954,1945+ 2022,2021 . (-1954,1945)`

`= 2022,2021 * [1954,1945 + (-1954,1945)]`

`= 2022,2021*0 `

`= 0`

`12)`

`-5,2 .72 +69,1 +5,2 . (-28)+(-1,1)`

`= -5,2*72 + 69,1 - 5,2*28 - 1,1`

`= -5,2*(72+28) + (69,1 - 1,1)`

`= -5,2*100 + 68`

`= -520 + 68`

`= -452`

`13)`

`(7 -1/2-3/4) : (5-1/4-5/8)`

`= 23/4 \div 33/8`

`=46/33`

`14)`

`(8+ 2 1/3 -3/5) -(5+0,4) -( 3 1/3 - 2)`

`= 8+ 2 1/3 - 3/5 - 5 - 0,4 - 3 1/3 + 2`

`= (8+2-5) + (2 1/3 - 3 1/3) - (0,6 + 0,4) `

`= 5 - 1 - 1`

`= 3`

help lười tính quá

a. |x-1/5|=|-5/2|-|1/4-2/3|

=> |x-1/5|=5/2-5/12

=> |x-1/5|=25/12

+) x-1/5=25/12

=> x=137/60

+) x-1/5=-25/12

=> x=-113/60

Vậy x \(\in\){-113/60 ; 137/60}

b. (x-0,5).(x²-1,96)=0

+) x-0,5=0

=> x=0,5

+) x²-1,96=0

=> x²=1,96

=> x²=(7/5)²=(-7/5)²

=> x \(\in\left\{-\frac{7}{5};\frac{7}{5}\right\}\)

Vậy \(x\in\left\{-\frac{7}{5};0,5;\frac{7}{5}\right\}\).

c. 5/6 : x = 20 : 3

=> 5/6 : x = 20/3

=> x = 5/6 : 20/3

=> x=1/8

Vậy x=1/8.

Minh Hiền làm đúng rồi tick cho bạn ý đi các bạn ơi ! ( mình ko tick được vì hết lượt rồi )

a= -8 phần 9

b= 2

a.A=-1/2-1/6-1/12-1/20-1/30-1/42-1/56-1/72=-151/180

Vậy A=151/180

b.B=0,5+0,4+1/3+1/6+5/7-4/35=2

Vậy B=2