tính nhanh 2155-(174 2155) (-68 174) 2.$\dfrac{3}{7}\left(\dfrac{2}{9}-1\dfrac{3}{7}\right)-\dfrac{5}{3}:\dfrac{1}{9}$ \(\left(1-\dfrac{1}{2}\right)\left(1-\dfrac{1}{3}\right)\left(1-\dfrac{1}{4}...

1

KS

Kim So Huyn

7 tháng 5 2017

2155-(174+2155)+(-68+174)=2155-174-2155-68+174

= -68

( 1 - $\dfrac{1}{2}$ ) ( 1- $\dfrac{1}{3}$) ( 1 - $\dfrac{1}{4}$) ( 1 - $\dfrac{1}{5}$) = $\dfrac{1}{2}.\dfrac{1}{3}.\dfrac{1}{4}.\dfrac{1}{5}$

= $\dfrac{1}{120}$

Mình ps có 2 câu à ^.^!

GL

Giang Lê

8 tháng 5 2017

cam on bn

KL

Khánh Linh

14 tháng 7 2017

BT2: Tính nhanh

7) $\left(-\dfrac{1}{2}\right)-\left(-\dfrac{3}{5}\right)+\left(-\dfrac{1}{9}\right)+\dfrac{1}{71}-\left(-\dfrac{2}{7}\right)+\dfrac{4}{35}-\dfrac{7}{18}$

8)$\left(3-\dfrac{1}{4}+\dfrac{2}{3}\right)-\left(5-\dfrac{1}{3}-\dfrac{6}{5}\right)-\left(6-\dfrac{7}{4}+\dfrac{3}{2}\right)$

1

LH

Lý Hoành Nghị

24 tháng 7 2017

Ôn tập toán 6

LG

Lưu Gia Lợi

20 tháng 5 2022

Tính giá trị của biểu...

1

NH

Nguyễn Hà Tuấn Hưng 7A14

20 tháng 5 2022

A= 4/7.

Biết có cái

KL

Khánh Linh

22 tháng 3 2017

Tính nhanh:

11) $\dfrac{5}{7}\left(\dfrac{1}{2}-\dfrac{1}{3}+\dfrac{4}{7}\right)+\left(\dfrac{1}{3}-\dfrac{1}{2}-\dfrac{4}{7}\right):\dfrac{7}{5}$

12)$\dfrac{43}{5}\left(\dfrac{17}{3}-\dfrac{16}{9}+2\right)-\dfrac{43}{5}\left(\dfrac{17}{3}-\dfrac{16}{9}\right)$

2

ND

Nguyễn Đắc Định

22 tháng 3 2017

11) $\dfrac{5}{7}\left(\dfrac{1}{2}-\dfrac{1}{3}+\dfrac{4}{7}\right)+\left(\dfrac{1}{3}-\dfrac{1}{2}-\dfrac{4}{7}\right):\dfrac{7}{5}$

= $\dfrac{5}{7}\left(\dfrac{1}{2}-\dfrac{1}{3}+\dfrac{4}{7}\right)+\left(\dfrac{1}{3}-\dfrac{1}{2}-\dfrac{4}{7}\right)\cdot\dfrac{5}{7}$

= $\dfrac{5}{7}\left(\dfrac{1}{2}-\dfrac{1}{3}+\dfrac{4}{7}+\dfrac{1}{3}-\dfrac{1}{2}-\dfrac{4}{7}\right)$

= $\dfrac{5}{7}\cdot0$

=0

12) $\dfrac{43}{5}\left(\dfrac{17}{3}-\dfrac{16}{9}+2\right)-\dfrac{43}{5}\left(\dfrac{17}{3}-\dfrac{16}{9}\right)$

= $\dfrac{43}{5}\left(\dfrac{17}{3}-\dfrac{16}{9}+2-\dfrac{17}{3}+\dfrac{16}{9}\right)$

= $\dfrac{43}{5}\cdot2=\dfrac{43}{10}$

PH

Phạm Hà Phương

25 tháng 7 2017

11, 5/7( 1/2-1/3+1/4)+ (1/3-1/2-1/4):7/5

= 5/7.(1/2 - 1/3 + 1/4 )+( 1/3 - 1/2 - 1/4). 5/7

= 5/7.(1/2 - 2/3 + 1/4 + 1/3 - 1/2 - 1/4)

= 5/7 . -1/3

= -5/21

12, 43/5.(17/3 - 16/9 + 2)- 43/5. (17/3 - 16/9)

= 43/5.( 17/3 - 16/9 + 2 - 17/3 + 16/9)

= 43/5 . 2

= 86/5

Tính giá trị của các biểu thức sau : a)$\left(7+3\dfrac{1}{4}-\dfrac{3}{5}\right)$+(0,4 - 5) - $\left(4\dfrac{1}{4}-1\right)$ b)$\dfrac{2}{3}$ - $\left[\left(-\dfrac{7}{4}\right)-\left(\dfrac{1}{2}+\dfrac{3}{8}\right)\right]$ c)$\left(9-\dfrac{1}{2}-\dfrac{3}{4}\right)$:$\left(7-\dfrac{1}{4}-\dfrac{5}{8}\right)$ d)3 - $\dfrac{1-\dfrac{1}{7}}{1+\dfrac{1}{7}}$ giúp mình nhé trả lời mình cho tick cảm ơn các bạn...

NT

Nguyễn Thị Mỹ Loan♍13/9

21 tháng 6 2023

Tính giá trị các biểu thức sau theo cách hợp lí nhất. a) $\mathrm{A}=\left(\dfrac{2}{7} \cdot \dfrac{1}{4}-\dfrac{1}{3} \cdot \dfrac{2}{7}\right):\left(\dfrac{2}{7} \cdot \dfrac{3}{9}-\dfrac{2}{7} \cdot \dfrac{2}{5}\right)$; b) $\mathrm{B}=\dfrac{\left(\dfrac{1}{5}-\dfrac{2}{7}\right) \cdot \dfrac{3}{4}-\dfrac{3}{4} \cdot\left(\dfrac{1}{3}-\dfrac{2}{7}\right)}{\dfrac{1}{5} \cdot \dfrac{2}{7}-\dfrac{1}{3} \cdot\left(\dfrac{2}{7}+\dfrac{3}{9}\right)+\dfrac{3}{9} \cdot \dfrac{1}{5}}...

1

TT

Thư Thư

21 tháng 6 2023

$a,\left(7+3\dfrac{1}{4}-\dfrac{3}{5}\right)+\left(0,4-5\right)-\left(4\dfrac{1}{4}-1\right)$

$=\left(7+\dfrac{13}{4}-\dfrac{3}{5}\right)-\dfrac{23}{5}-\left(\dfrac{17}{4}-1\right)$

$=7+\dfrac{13}{4}-\dfrac{3}{5}-\dfrac{23}{5}-\dfrac{17}{4}+1$

$=\left(7+1\right)+\left(\dfrac{13}{4}-\dfrac{17}{4}\right)-\left(\dfrac{3}{5}+\dfrac{23}{5}\right)$

$=8-\dfrac{4}{4}-\dfrac{26}{5}$

$=7-\dfrac{26}{5}$

$=\dfrac{9}{5}$

$b,\dfrac{2}{3}-\left[\left(-\dfrac{7}{4}\right)-\left(\dfrac{1}{2}+\dfrac{3}{8}\right)\right]$

$=\dfrac{2}{3}-\left(-\dfrac{7}{4}-\dfrac{1}{2}-\dfrac{3}{8}\right)$

$=\dfrac{2}{3}-\left(-\dfrac{14}{8}-\dfrac{4}{8}-\dfrac{3}{8}\right)$

$=\dfrac{2}{3}-\left(-\dfrac{21}{8}\right)$

$=\dfrac{2}{3}+\dfrac{21}{8}$

$=\dfrac{79}{24}$

$c,\left(9-\dfrac{1}{2}-\dfrac{3}{4}\right):\left(7-\dfrac{1}{4}-\dfrac{5}{8}\right)$

$=\left(\dfrac{36}{4}-\dfrac{2}{4}-\dfrac{3}{4}\right):\left(\dfrac{56}{8}-\dfrac{2}{8}-\dfrac{5}{8}\right)$

$=\dfrac{31}{4}:\dfrac{49}{8}$

$=\dfrac{62}{49}$

$d,3-\dfrac{1-\dfrac{1}{7}}{1+\dfrac{1}{7}}=3-\dfrac{\dfrac{7}{7}-\dfrac{1}{7}}{\dfrac{7}{7}+\dfrac{1}{7}}=3-\left(\dfrac{6}{7}:\dfrac{8}{7}\right)=3-\dfrac{3}{4}=\dfrac{9}{4}$

Đúng(5)

TD

Thầy Đức Anh

Giáo viên VIP

27 tháng 4 2022

12

PT

Phạm Trường Giang

VIP

22 tháng 6 2022

a) $A = [\frac{2}{7} (\frac{1}{4} - \frac{1}{3})] : [\frac{2}{7} (\frac{1}{3} - \frac{2}{5})] = (\frac{1}{4} - \frac{1}{3}) : (\frac{1}{3} - \frac{2}{5}) = 1 \frac{1}{4}$ .
b) $B = \frac{\frac{3}{4} (\frac{1}{5} - \frac{2}{7} - \frac{1}{3} + \frac{2}{7})}{\frac{1}{5} (\frac{2}{7} + \frac{1}{3}) - \frac{1}{3} (\frac{2}{7} + \frac{1}{3})} = \frac{\frac{3}{4} (\frac{1}{5} - \frac{1}{3})}{(\frac{1}{5} - \frac{1}{3}) (\frac{2}{7} + \frac{1}{3})} = 1 \frac{11}{52}$ .

T

TINH

13 tháng 7 2022

a) $\mathrm{A}=\left[\dfrac{2}{7}\left(\dfrac{1}{4}-\dfrac{1}{3}\right)\right]:\left[\dfrac{2}{7}\left(\dfrac{1}{3}-\dfrac{2}{5}\right)\right]=\left(\dfrac{1}{4}-\dfrac{1}{3}\right):\left(\dfrac{1}{3}-\dfrac{2}{5}\right)=1 \dfrac{1}{4}$ .
b) $\mathrm{B}=\dfrac{\dfrac{3}{4}\left(\dfrac{1}{5}-\dfrac{2}{7}-\dfrac{1}{3}+\dfrac{2}{7}\right)}{\dfrac{1}{5}\left(\dfrac{2}{7}+\dfrac{1}{3}\right)-\dfrac{1}{3}\left(\dfrac{2}{7}+\dfrac{1}{3}\right)}=\dfrac{\dfrac{3}{4}\left(\dfrac{1}{5}-\dfrac{1}{3}\right)}{\left(\dfrac{1}{5}-\dfrac{1}{3}\right)\left(\dfrac{2}{7}+\dfrac{1}{3}\right)}=1 \dfrac{11}{52}$

NK

Nezuko Kamado

29 tháng 10 2021

Tìm x :

1) $\left(-0,75x+\dfrac{5}{2}\right).\dfrac{4}{7}-\left(-\dfrac{1}{3}\right)=-\dfrac{5}{6}$

2) $\left(4x-9\right)\left(2,5+\dfrac{-7}{3}x\right)=0$

3) $\left|x-\dfrac{3}{4}\right|-\dfrac{1}{2}=0$

4)$\left(\dfrac{3}{5}-\dfrac{2}{3}x\right)^3=\dfrac{-64}{125}$

1

NL

Nguyễn Lê Phước Thịnh

29 tháng 10 2021

3: $\left|x-\dfrac{3}{4}\right|-\dfrac{1}{2}=0$

$\Leftrightarrow\left|x-\dfrac{3}{4}\right|=\dfrac{1}{2}$

$\Leftrightarrow\left[{}\begin{matrix}x-\dfrac{3}{4}=\dfrac{1}{2}\\x-\dfrac{3}{4}=-\dfrac{1}{2}\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=\dfrac{5}{4}\\x=\dfrac{1}{4}\end{matrix}\right.$

Đúng(2)

HV

Hoa Vô Khuyết

28 tháng 7 2023

tính
a,$6\dfrac{4}{5}-\left(1\dfrac{2}{3}+3\dfrac{4}{5}\right)$
b,$7\dfrac{5}{9}-\left(2\dfrac{3}{4}+3\dfrac{5}{9}\right)$
c,$6\dfrac{7}{7}-\left(1\dfrac{3}{4}+2\dfrac{5}{7}\right)$

1

NL

Nguyễn Lê Phước Thịnh

28 tháng 7 2023

a: $=6+\dfrac{4}{5}-1-\dfrac{2}{3}-3-\dfrac{4}{5}$

$=2-\dfrac{2}{3}=\dfrac{4}{3}$

b: $=7+\dfrac{5}{9}-2-\dfrac{3}{4}-3-\dfrac{5}{9}=2-\dfrac{3}{4}=\dfrac{5}{4}$

c: =6+7/7-1-3/4-2-5/7

=3+2/7-3/4

=84/28+8/28-21/28

=84/28-13/28

=71/28

DD

Đỗ Diệu Linh

13 tháng 9 2017

Tinh

$\dfrac{\left(1+2+3+...+100\right)\left(\dfrac{1}{3}-\dfrac{1}{5}-\dfrac{1}{7}-\dfrac{1}{9}\right)\left(6,3.12-21.36\right)}{\dfrac{1}{2}+\dfrac{1}{3}+\dfrac{1}{4}+...+\dfrac{1}{100}}$

$\dfrac{\left(\dfrac{3}{10}-\dfrac{4}{15}-\dfrac{7}{20}\right).\dfrac{5}{9}}{\left(\dfrac{1}{14}+\dfrac{1}{7}-\dfrac{-3}{35}\right)\dfrac{-4}{3}}$

2

NT

Nguyễn Thanh Hằng

13 tháng 9 2017

a/ $\dfrac{\left(1+2+.....+100\right)\left(\dfrac{1}{3}-\dfrac{1}{5}-\dfrac{1}{7}-\dfrac{1}{9}\right)\left(6,3.12-21.36\right)}{\dfrac{1}{2}+\dfrac{1}{3}+.......+\dfrac{1}{100}}$

$=\dfrac{\left(1+2+3+.....+100\right)\left(\dfrac{1}{3}-\dfrac{1}{5}-\dfrac{1}{7}-\dfrac{1}{9}\right).0}{\dfrac{1}{2}+\dfrac{1}{3}+.......+\dfrac{1}{100}}$

$=\dfrac{0}{\dfrac{1}{2}+\dfrac{1}{3}+.....+\dfrac{1}{100}}$

$=0$

TT

Trần Thị Hương

13 tháng 9 2017

bn có chép sai đề bài ko vậy

TN

Tiên Nữ Bedee

12 tháng 5 2021

a, $\dfrac{1}{3}-\dfrac{1}{4}:\dfrac{2}{5}$

b, $\dfrac{6}{7}-\left(\dfrac{5}{6}+\dfrac{1}{3}\right)-\left(\dfrac{2}{3}+\dfrac{1}{7}\right)$

c, $\dfrac{-5}{9}.\dfrac{2}{5}+4\dfrac{5}{9}+\dfrac{5}{9}.\dfrac{-3}{5}$

d, $3\dfrac{1}{2}-\left(5\dfrac{4}{7}-1\dfrac{1}{2}\right):0,75$

2

TA

Trần Ái Linh

12 tháng 5 2021

a) `1/3 - 1/4 : 2/5 = 1/3 - 5/8 = -7/24`

b) `6/7-(5/6+1/3)-(2/3+1/7) = 6/7-5/6-1/3-2/3-1/7`

`=(6/7-1/7)-(1/3+2/3)-5/6`

`=5/7-1-5/6`

`=-47/42`

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

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

`=-5/9 . (2/5 + 3/5-1) + 4`

`=-5/9 . 0 +4`

`=4`

d) 3 1/2 - (5 4/7 - 1 1/2) : 0,75`

`=7/2 - (39/7 - 3/2) : 3/4`

`= 7/2 - 57/14 : 3/4`

`=7/2 - 38/7`

`=-27/14`

Đúng(2)

NK

Nguyễn Kiều Trang

16 tháng 6 2021

De tke nma khonq bt lamm

Nguu