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} \cd...

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) $\mathrm{B}=\dfrac{\dfrac{3}{4}\left(\dfrac{1}{5}-\dfrac{2}{7}-\dfrac{1}{3}+\dfrac{2}{7}\right)}{\dfrac{1}{5}\left(\dfrac{2}{7}+\dfrac{1}{3}\right)-\dfrac{1}{3}\left(\dfrac{2}{7}+\dfrac{1}{3}\right)}=\dfrac{\dfrac{3}{4}\left(\dfrac{1}{5}-\dfrac{1}{3}\right)}{\left(\dfrac{1}{5}-\dfrac{1}{3}\right)\left(\dfrac{2}{7}+\dfrac{1}{3}\right)}=1 \dfrac{11}{52}$

Tính giá trí của biểu thức sau theo cách hợp lí nhất. a) $\mathrm{A}=\dfrac{3}{5} \cdot \dfrac{6}{7}+\dfrac{3}{7}: \dfrac{5}{3}-\dfrac{2}{7}: 1 \dfrac{2}{3}$; b) $\mathrm{B}=\left(-13 \cdot \dfrac{2}{5}+\dfrac{-2}{9}: 2 \dfrac{1}{2}+\dfrac{2}{5}. \dfrac{11}{9}\right) \cdot 2 \dfrac{1}{2}$; c) $\mathrm{C}=\left(\dfrac{-4}{5}+\dfrac{5}{7}\right): \dfrac{2}{3}+\left(\dfrac{-1}{5}+\dfrac{2}{7}\right): \dfrac{2}{3}$; d)...

TD

Thầy Đức Anh

Giáo viên VIP

27 tháng 4 2022

14

PT

Phạm Trường Giang

VIP

22 tháng 6 2022

a) $A = \frac{3}{5} . \frac{6}{7} + \frac{3}{7} . \frac{3}{5} - \frac{2}{7} . \frac{3}{5}$
$= \frac{3}{5} \cdot (\frac{6}{7} + \frac{3}{7} - \frac{2}{7}) = \frac{3}{5}$
b) $B = (- 13 \cdot \frac{2}{5} + \frac{- 2}{9} \cdot \frac{2}{5} + \frac{2}{5} \cdot \frac{11}{9}) \cdot \frac{5}{2}$
$= (- 13 - \frac{2}{9} + \frac{11}{9}) \cdot \frac{2}{5} \cdot \frac{5}{2} = - 13 + (\frac{11}{9} - \frac{2}{9}) = - 12 .$
c) $C = (\frac{- 4}{5} + \frac{5}{7}) \cdot \frac{3}{2} + (\frac{- 1}{5} + \frac{2}{7}) \cdot \frac{3}{2} = (\frac{- 4}{5} + \frac{5}{7} + \frac{- 1}{5} + \frac{2}{7}) \cdot \frac{3}{2} = ((\frac{- 4}{5} + \frac{- 1}{5}) + (\frac{5}{7} + \frac{2}{7})) \cdot \frac{3}{2} = 0 .$
d) $D = \frac{4}{9} : (\frac{1}{15} - \frac{10}{15}) + \frac{4}{9} : (\frac{2}{22} - \frac{5}{22})$
$= \frac{4}{9} : \frac{- 3}{5} + \frac{4}{9} : \frac{- 3}{22} = \frac{4}{9} \cdot \frac{- 5}{3} + \frac{4}{9} . \frac{- 22}{3}$
$= \frac{4}{9} \cdot (\frac{- 5}{3} + \frac{- 22}{3}) = \frac{4}{9} . \frac{- 27}{3} = - 4 .$

T

TINH

13 tháng 7 2022

a) $\mathrm{A}=\dfrac{3}{5}. \dfrac{6}{7}+\dfrac{3}{7}. \dfrac{3}{5}-\dfrac{2}{7}. \dfrac{3}{5}$

b) $\mathrm{B} =\left(-13 \cdot \dfrac{2}{5}+\dfrac{-2}{9} \cdot \dfrac{2}{5}+\dfrac{2}{5} \cdot \dfrac{11}{9}\right) \cdot \dfrac{5}{2}$
$=\left(-13-\dfrac{2}{9}+\dfrac{11}{9}\right) \cdot \dfrac{2}{5} \cdot \dfrac{5}{2}=-13+\left(\dfrac{11}{9}-\dfrac{2}{9}\right)=-12 .$
c) $\mathrm{C} =\left(\dfrac{-4}{5}+\dfrac{5}{7}\right) \cdot \dfrac{3}{2}+\left(\dfrac{-1}{5}+\dfrac{2}{7}\right) \cdot \dfrac{3}{2} =\left(\dfrac{-4}{5}+\dfrac{5}{7}+\dfrac{-1}{5}+\dfrac{2}{7}\right) \cdot \dfrac{3}{2}=\left(\left(\dfrac{-4}{5}+\dfrac{-1}{5}\right)+\left(\dfrac{5}{7}+\dfrac{2}{7}\right)\right) \cdot \dfrac{3}{2}=0 .$
d) $\mathrm{D}=\dfrac{4}{9}:\left(\dfrac{1}{15}-\dfrac{10}{15}\right)+\dfrac{4}{9}:\left(\dfrac{2}{22}-\dfrac{5}{22}\right)$

Tính giá trị của các biểu thức sau 1) $A=1+2+2^2+...+2^{2015}$ 2) $B=\left(\dfrac{1}{4}-1\right)\cdot\left(\dfrac{1}{9}-1\right)\cdot\left(\dfrac{1}{16}-1\right)\cdot\cdot\cdot\cdot\cdot\left(\dfrac{1}{400}-1\right)$ 3) $C=\left(\dfrac{1}{4\cdot9}+\dfrac{1}{9\cdot14}+\dfrac{1}{14\cdot19}+...+\dfrac{1}{44\cdot49}\right)\cdot\dfrac{1-3-5-7-...-49}{89}$ 4)...

XN

Xử Nữ Chính Là Tôi

15 tháng 11 2017

0

NA

Nguyễn An Vy

2 tháng 8 2017

a) $\dfrac{\left(x+\dfrac{3}{4}\right)\cdot\dfrac{7}{2}-\dfrac{1}{6}}{-\left(\dfrac{4}{5}+\dfrac{1}{3}\right)\cdot\dfrac{1}{2}+1}=2\dfrac{33}{52}$

b)$\dfrac{\left(5-\dfrac{2}{7}\right)\cdot\dfrac{7}{9}\cdot\dfrac{3}{5}}{\left(3x-\dfrac{5}{6}\right):\dfrac{1}{7}}=5\dfrac{5}{21}$

7

G

Giang

2 tháng 8 2017

Giải:

a) $\dfrac{\left(x+\dfrac{3}{4}\right).\dfrac{7}{2}-\dfrac{1}{6}}{-\left(\dfrac{4}{5}+\dfrac{1}{3}\right).\dfrac{1}{2}+1}=2\dfrac{33}{52}$

$\Leftrightarrow\dfrac{\left(x+\dfrac{3}{4}\right).\dfrac{7}{2}-\dfrac{1}{6}}{-\dfrac{17}{15}.\dfrac{1}{2}+1}=\dfrac{137}{52}$

$\Leftrightarrow\dfrac{\left(x+\dfrac{3}{4}\right).\dfrac{7}{2}-\dfrac{1}{6}}{\dfrac{13}{30}}=\dfrac{137}{52}$

$\Leftrightarrow\left(x+\dfrac{3}{4}\right).\dfrac{7}{2}-\dfrac{1}{6}=\dfrac{137}{52}.\dfrac{13}{30}$

$\Leftrightarrow\left(x+\dfrac{3}{4}\right).\dfrac{7}{2}-\dfrac{1}{6}=\dfrac{137}{120}$

$\Leftrightarrow\left(x+\dfrac{3}{4}\right).\dfrac{7}{2}=\dfrac{137}{120}+\dfrac{1}{6}$

$\Leftrightarrow\left(x+\dfrac{3}{4}\right).\dfrac{7}{2}=\dfrac{157}{120}$

$\Leftrightarrow x+\dfrac{3}{4}=\dfrac{157}{120}:\dfrac{7}{2}$

$\Leftrightarrow x+\dfrac{3}{4}=\dfrac{157}{420}$

$\Leftrightarrow x=\dfrac{157}{420}-\dfrac{3}{4}$

$\Leftrightarrow x=-\dfrac{79}{210}$

Vậy $x=-\dfrac{79}{210}$.

b) $\dfrac{\left(5-\dfrac{2}{7}\right).\dfrac{7}{9}.\dfrac{3}{5}}{\left(3x-\dfrac{5}{6}\right):\dfrac{1}{7}}=5\dfrac{5}{21}$

$\Leftrightarrow\dfrac{\left(5-\dfrac{2}{7}\right).\dfrac{7}{15}}{\left(3x-\dfrac{5}{6}\right):\dfrac{1}{7}}=\dfrac{110}{21}$

$\Leftrightarrow\dfrac{\dfrac{33}{7}.\dfrac{7}{15}}{\left(3x-\dfrac{5}{6}\right):\dfrac{1}{7}}=\dfrac{110}{21}$

$\Leftrightarrow\dfrac{\dfrac{11}{5}}{\left(3x-\dfrac{5}{6}\right):\dfrac{1}{7}}=\dfrac{110}{21}$

$\Leftrightarrow\left(3x-\dfrac{5}{6}\right):\dfrac{1}{7}=\dfrac{11}{5}:\dfrac{110}{21}$

$\Leftrightarrow\left(3x-\dfrac{5}{6}\right):\dfrac{1}{7}=\dfrac{21}{50}$

$\Leftrightarrow3x-\dfrac{5}{6}=\dfrac{21}{50}.\dfrac{1}{7}$

$\Leftrightarrow3x-\dfrac{5}{6}=\dfrac{3}{50}$

$\Leftrightarrow3x=\dfrac{3}{50}+\dfrac{5}{6}$

$\Leftrightarrow3x=\dfrac{67}{75}$

$\Leftrightarrow x=\dfrac{67}{75}:3$

$\Leftrightarrow x=\dfrac{67}{225}$

Vậy $x=\dfrac{67}{225}$.

Chúc bạn học tốt!

NA

Nguyễn An Vy

2 tháng 8 2017

CÁC BẠN GIÚP MK NHA!!!

NGÀY MAI MK NỘP BÀI RỒI

AI TRẢ LỜI NHANH NHẤT

CHÍNH XÁC NHẤT VÀ RÕ RÀNG

THÌ MK TICK CHO NHA!!!

NHỚ TRẢ LỜI NHANH GIÙM MK NHA

Tính giá trị của các biểu thức...

XN

Xử Nữ Chính Là Tôi

15 tháng 11 2017

0

TL

Thu Linh

20 tháng 1 2022

Tính các biểu thức sau :
$\dfrac{a.\left(7\cdot x^2+11\cdot y^2\right)}{\left(14\cdot x^{12}-11\cdot y^2\right)}.\left(\dfrac{x}{11}\right)=\left(\dfrac{y}{7}\right)$

0

AT

Ai thích tui

4 tháng 5 2022

tính giá trị biểu thức

$\dfrac{3}{5}x\dfrac{2}{3}:\dfrac{1}{2}=?$

$\dfrac{2}{3}\cdot\dfrac{1}{2}+\dfrac{1}{3}=?$

$\left(\dfrac{5}{7}+\dfrac{2}{5}\right):\dfrac{11}{7}=?$

#Toán lớp 5

3

HD

Hải Đăng Nguyễn

4 tháng 5 2022

1.$\dfrac{4}{5}$

2.$\dfrac{2}{3}$

3.$\dfrac{39}{55}$

Đúng(1)

AT

Ai thích tui

4 tháng 5 2022

cách làm

TD

Thầy Đức Anh

Giáo viên VIP

29 tháng 11 2023

(1,5 điểm)Thực hiện phép tính:

a) $\dfrac{3}{4}+1 \dfrac{2}{3}-\dfrac{7}{9}$;

b) $\dfrac{1}{7} \cdot \left(\dfrac{4}{3}\right)^2-\dfrac{1}{7}: \dfrac{9}{11}$;

c) $0,5 \cdot \dfrac{4}{9}+\left(\dfrac{1}{3}-1,5\right)^2-\left(\dfrac{2}{3}\right)^9:\left(\dfrac{2}{3}\right)^7$.

Tính giá trị biểu thức : 1. $A=\dfrac{\dfrac{2}{5}+\dfrac{2}{7}-\dfrac{2}{9}-\dfrac{2}{11}}{\dfrac{4}{5}+\dfrac{4}{7}-\dfrac{4}{9}-\dfrac{4}{11}}$ 2. $B=\dfrac{1^2}{1\cdot2}\cdot\dfrac{2^2}{2\cdot3}\cdot\dfrac{3^2}{3\cdot4}\cdot\dfrac{4^2}{4\cdot5}$ 3. $C=\dfrac{2^2}{1\cdot3}\cdot\dfrac{3^2}{2\cdot4}\cdot\dfrac{4^2}{3\cdot5}\cdot\dfrac{5^2}{4\cdot6}\cdot\dfrac{5^2}{4\cdot6}$ 4. $D=\left(\dfrac{4}{5}-\dfrac{1}{6}\right)\cdot\left(\dfrac{2}{3}\cdot\dfrac{1}{4}\right)^2$ 5. Cho...

0

NV

Nguyễn Vũ Hoàng

27 tháng 11 2017

Tính giá trị biểu thức :

1. $A=\dfrac{\dfrac{2}{5}+\dfrac{2}{7}-\dfrac{2}{9}-\dfrac{2}{11}}{\dfrac{4}{5}+\dfrac{4}{7}-\dfrac{4}{9}-\dfrac{4}{11}}$

2. $B=\dfrac{1^2}{1\cdot2}\cdot\dfrac{2^2}{2\cdot3}\cdot\dfrac{3^2}{3\cdot4}\cdot\dfrac{4^2}{4\cdot5}$

3. $C=\dfrac{2^2}{1\cdot3}\cdot\dfrac{3^2}{2\cdot4}\cdot\dfrac{4^2}{3\cdot5}\cdot\dfrac{5^2}{4\cdot6}\cdot\dfrac{5^2}{4\cdot6}$

4. $D=\left(\dfrac{4}{5}-\dfrac{1}{6}\right)\cdot\left(\dfrac{2}{3}\cdot\dfrac{1}{4}\right)^2$

5. Cho $M=8\dfrac{2}{7}-\left(3\dfrac{4}{9}+4\dfrac{2}{7}\right)$ ; $N=\left(10\dfrac{2}{9}+2\dfrac{3}{5}\right)-6\dfrac{2}{9}$. Tính $P=M-N$

6. $E=10101\left(\dfrac{5}{111111}+\dfrac{5}{222222}-\dfrac{4}{3\cdot7\cdot11\cdot13\cdot37}\right)$

7. $F=\dfrac{\dfrac{1}{3}+\dfrac{1}{7}-\dfrac{1}{13}}{\dfrac{2}{3}+\dfrac{2}{7}-\dfrac{2}{13}}\cdot\dfrac{\dfrac{3}{4}-\dfrac{3}{16}-\dfrac{3}{256}+\dfrac{3}{64}}{1-\dfrac{1}{4}+\dfrac{1}{16}-\dfrac{1}{64}}+\dfrac{5}{8}$

8. $G=\text{[}\dfrac{\left(6-4\dfrac{1}{2}\right):0,03}{\left(3\dfrac{1}{20}-2,65\right)\cdot4+\dfrac{2}{5}}-\dfrac{\left(0,3-\dfrac{3}{20}\right)\cdot1\dfrac{1}{2}}{\left(1,88+2\dfrac{3}{25}\right)\cdot\dfrac{1}{80}}\text{]}:\dfrac{49}{60}$

9. $H=\dfrac{1}{1\cdot2\cdot3}+\dfrac{1}{2\cdot3\cdot4}+\dfrac{1}{4\cdot5\cdot6}+...+\dfrac{1}{98\cdot99\cdot100}$

10. $I=\dfrac{8}{9}\cdot\dfrac{15}{16}\cdot\dfrac{24}{25}\cdot...\cdot\dfrac{2499}{2500}$

11. $K=\left(-1\dfrac{1}{2}\right)\left(-1\dfrac{1}{3}\right)\left(-1\dfrac{1}{4}\right)...\left(-1\dfrac{1}{999}\right)$

12. $L=1\dfrac{1}{3}+1\dfrac{1}{8}+1\dfrac{1}{15}...$ (98 thừa số)

13. $M=-2+\dfrac{1}{-2+\dfrac{1}{-2+\dfrac{1}{-2+\dfrac{1}{3}}}}$

14. $N=\dfrac{155-\dfrac{10}{7}-\dfrac{5}{11}+\dfrac{5}{23}}{403-\dfrac{26}{7}-\dfrac{13}{11}+\dfrac{13}{23}}$

15. $P=\left(\dfrac{1}{4}-1\right)\left(\dfrac{1}{5}-1\right)...\left(\dfrac{1}{2001}-1\right)$

16. $Q=\left(\dfrac{1}{1\cdot2}+\dfrac{1}{3\cdot4}+\dfrac{1}{4\cdot5}+...+\dfrac{1}{2005\cdot2006}\right):\left(\dfrac{1}{1004\cdot2006}+\dfrac{1}{1005\cdot2005}+...+\dfrac{1}{2006\cdot1004}\right)$

#Toán lớp 6

2

QH

Quang Ho Si

27 tháng 11 2017

1. $A=\dfrac{2\left(\dfrac{1}{5}+\dfrac{1}{7}-\dfrac{1}{9}-\dfrac{1}{11}\right)}{4\left(\dfrac{1}{5}+\dfrac{1}{7}-\dfrac{1}{9}-\dfrac{1}{11}\right)}=\dfrac{2}{4}=\dfrac{1}{2}$

2. $B=\dfrac{1^2.2^2.3^2.4^2}{1.2^2.3^2.4^2.5}=\dfrac{1}{5}$

3.$C=\dfrac{2^2.3^2.\text{4^2.5^2}.5^2}{1.2^2.3^2.4^2.5.6^2}=\dfrac{125}{36}$

4.D=$D=\left(\dfrac{4}{5}-\dfrac{1}{6}\right).\dfrac{4}{9}.\dfrac{1}{16}=\dfrac{19}{30}.\dfrac{1}{36}=\dfrac{19}{1080}$

NA

Nguyễn Anh Quang

29 tháng 4 2022

hôi lì sít

NA

Nguyễn An Vy

2 tháng 8 2017

a)$\dfrac{\left(x+\dfrac{3}{4}\right)\cdot\dfrac{7}{2}-\dfrac{1}{6}}{-\left(\dfrac{4}{5}+\dfrac{1}{3}\right)\cdot\dfrac{1}{2}+1}=2\dfrac{33}{52}$

b)$\dfrac{\left(5-\dfrac{2}{7}\right)\cdot\dfrac{7}{9}:\dfrac{3}{5}}{\left(3x-\dfrac{5}{6}\right):\dfrac{1}{7}}=5\dfrac{5}{21}$

Bài 7: Tìm X

2

NA

Nguyễn An Vy

2 tháng 8 2017

Hoàng Ngọc Anh bài này nè bn giúp mk nha!!! ngày mai mk phải nộp bài rùi =.=

HT

Hoàng Thị Ngọc Anh

2 tháng 8 2017

a) $\Rightarrow\dfrac{\dfrac{7}{2}x+\dfrac{59}{24}}{\dfrac{13}{30}}=\dfrac{137}{52}$

$\Rightarrow\left(\dfrac{7}{2}x+\dfrac{59}{24}\right).52=\dfrac{13}{30}.137$

$\Rightarrow182x+\dfrac{767}{6}=\dfrac{1781}{30}$

$\Rightarrow x=\dfrac{-79}{210}$

b) Tương tự câu a)