Tìm x:a, x 30%x = -1,31b,\(\left(x-\frac{1}{2}\right):\frac{1}{3} \frac{5}{7}=9\frac{5}{7}\)c, \(\frac{1}{2}x-\frac{3}{4}=\frac{14}{9}.\frac{3}{7}\)d,\(\frac{-5}{6}-x=\frac{7}{12} \frac{-1}{3}\)e,\(...

9

GT

ღᏠᎮღ🅼🅸🅽🅷ঔ🅽🅶ụ🆈ঌ__[ᴅʀᴇᴀм тᴇᴀм]__

18 tháng 4 2019

\(a)x+30\%x=-1,31\)

\(\Leftrightarrow x+\frac{3x}{10}=-1,31\)

\(\Leftrightarrow10x+3x=-13,1\)

\(\Leftrightarrow13x=-13,1\Leftrightarrow x=-\frac{131}{130}\)

GT

ღᏠᎮღ🅼🅸🅽🅷ঔ🅽🅶ụ🆈ঌ__[ᴅʀᴇᴀм тᴇᴀм]__

18 tháng 4 2019

\(b)\left(x-\frac{1}{2}\right):\frac{1}{3}+\frac{5}{7}=9\frac{5}{7}\)

\(\Leftrightarrow\frac{2x-1}{2}.3+\frac{5}{7}=\frac{68}{7}\)

\(\Leftrightarrow\frac{6x-3}{2}=\frac{63}{7}\)

\(\Leftrightarrow\frac{6x-3}{2}=9\)

\(\Leftrightarrow6x-3=18\)

\(\Leftrightarrow x=\frac{7}{2}\)

QT

Quoc Tran Anh Le

Giáo viên

19 tháng 9 2023

Tìm x, biết:

a)\(x.\frac{{14}}{{27}} = \frac{{ - 7}}{9}\)

b)\(\left( {\frac{{ - 5}}{9}} \right):x = \frac{2}{3};\)

c)\(\frac{2}{5}:x = \frac{1}{{16}}:0,125\)

d)\( - \frac{5}{{12}}x = \frac{2}{3} - \frac{1}{2}\)

#Toán lớp 7

1

HQ

Hà Quang Minh

Giáo viên

19 tháng 9 2023

a)

\(\begin{array}{l}x.\frac{{14}}{{27}} = \frac{{ - 7}}{9}\\x = \frac{{ - 7}}{9}:\frac{{14}}{{27}}\\x = \frac{{ - 7}}{9}.\frac{{27}}{{14}}\\x = \frac{{ - 3}}{2}\end{array}\)

Vậy \(x = \frac{{ - 3}}{2}\).

b)

\(\begin{array}{l}\left( {\frac{{ - 5}}{9}} \right):x = \frac{2}{3}\\x = \left( {\frac{{ - 5}}{9}} \right):\frac{2}{3}\\x = \left( {\frac{{ - 5}}{9}} \right).\frac{3}{2}\\x = \frac{{ - 5}}{6}\end{array}\)

Vậy \(x = \frac{{ - 5}}{6}\).

c)

\(\begin{array}{l}\frac{2}{5}:x = \frac{1}{{16}}:0,125\\\frac{2}{5}:x = \frac{1}{{16}}:\frac{1}{8}\\\frac{2}{5}:x = \frac{1}{{16}}.8\\\frac{2}{5}:x = \frac{1}{2}\\x = \frac{2}{5}:\frac{1}{2}\\x = \frac{2}{5}.2\\x = \frac{4}{5}\end{array}\)

Vậy \(x = \frac{4}{5}\)

d)

\(\begin{array}{l} - \frac{5}{{12}}x = \frac{2}{3} - \frac{1}{2}\\ - \frac{5}{{12}}x = \frac{4}{6} - \frac{3}{6}\\ - \frac{5}{{12}}x = \frac{1}{6}\\x = \frac{1}{6}:\left( { - \frac{5}{{12}}} \right)\\x = \frac{1}{6}.\frac{{ - 12}}{5}\\x = \frac{{ - 2}}{5}\end{array}\)

Vậy \(x = \frac{{ - 2}}{5}\).

Chú ý: Khi trình bày lời giải bài tìm x, sau khi tính xong, ta phải kết luận.

HA

Hoàng Anh Thu

29 tháng 4 2018

bài 2 tìm...

1) Giải các pt sau: a) \(\frac{x-3}{5}=6-\frac{1-2x}{3}\) b) \(\frac{3x-2}{6}-5=\frac{3-2\left(x+7\right)}{4}\) c) \(\frac{x+8}{6}-\frac{2x-5}{5}=\frac{x-1}{3}-x+7\) d) \(\frac{7x}{8}-5\left(x-9\right)=\frac{2x+1,5}{6}\) e) \(\frac{5\left(x-1\right)+2}{6}-\frac{7x-1}{4}=\frac{2\left(2x+1\right)}{7}-5\) f)...

0

AT

ánh tuyết nguyễn

8 tháng 2 2020

#Toán lớp 8

1

XU

Xích U Lan

8 tháng 2 2020

a, \(\frac{x-3}{5}\) = 6 - \(\frac{1-2x}{3}\)

⇔ 3(x - 3) = 90 - 5(1 - 2x)

⇔ 3x - 9 = 90 - 5 + 10x

⇔ 3x - 10x = 90 - 5 + 9

⇔ -7x = 94

⇔ x = \(\frac{-94}{7}\)

S = { \(\frac{-94}{7}\) }

b, \(\frac{3x-2}{6}\) - 5 = \(\frac{3-2\left(x+7\right)}{4}\)

⇔ 2(3x - 2) - 60 = 9 - 6(x + 7)

⇔ 6x - 4 - 60 = 9 - 6x - 42

⇔ 6x + 6x = 9 - 42 + 60 + 4

⇔ 12x = 31

⇔ x = \(\frac{31}{12}\)

S = { \(\frac{31}{12}\) }

c, \(\frac{x+8}{6}\) - \(\frac{2x-5}{5}\) = \(\frac{x+1}{3}\) - x + 7

⇔ 5(x+ 8) - 6(2x - 5) = 10(x+1) - 30x+210

⇔ 5x+ 40 - 12x+ 30 = 10x+ 10 - 30x+210

⇔ 5x - 12x - 10x+ 30x = 10+ 210 - 30- 40

⇔ 13x = 150

⇔ x = \(\frac{150}{13}\)

S = { \(\frac{150}{13}\) }

d, \(\frac{7x}{8}\) - 5(x - 9) = \(\frac{2x+1,5}{6}\)

⇔ 21x - 120(x - 9) = 4(2x + 1,5)

⇔ 21x - 120x + 1080 = 8x + 6

⇔ 21x - 120x - 8x = 6 - 1080

⇔ -107x = -1074

⇔ x = \(\frac{1074}{107}\)

S = { \(\frac{1074}{107}\) }

e, \(\frac{5\left(x-1\right)+2}{6}\) - \(\frac{7x-1}{4}\) = \(\frac{2\left(2x+1\right)}{7}\) - 5

⇔ 140(x-1)+56 - 42(7x-1) = 48(2x+1)-840

⇔ 140x -140+56 -294x+42= 96x+48 -840

⇔ 140x -294x -96x = 48 -840 -42 -56+140

⇔ -250x = -750

⇔ x = 3

S = { 3 }

f, \(\frac{x+1}{3}\) + \(\frac{3\left(2x+1\right)}{4}\) = \(\frac{2x+3\left(x+1\right)}{6}\) + \(\frac{7+12x}{12}\)

⇔ 4(x+1)+9(2x+1) = 4x+6(x+1)+7+12x

⇔ 4x+4+18x+9 = 4x+6x+6+7+12x

⇔ 4x+18x - 4x - 6x - 12x = 6+7- 9 - 4

⇔ 0x = 0

S = R

Chúc bạn học tốt !

VN

Võ Ngọc Huyền

22 tháng 4 2020

Bạn ơi giải giúp mình 2 bài này với ạ : https://hoc24.vn/hoi-dap/question/969683.html

Mình cảm ơn trước nhaa

Tìm xa) x + 30 % . x = -1,1b) \(\left(x-\frac{1}{2}\right):\frac{1}{3}+\frac{5}{7}=9\frac{5}{7}\)c) \(\frac{-5}{6}-x=\frac{7}{12}+\frac{-1}{3}\)d) \(\frac{x+3}{-15}=\frac{1}{3}\)e) ( 4,5 - 2x) . \(\left(-1\frac{4}{7}\right)=\frac{11}{14}\)GIÚP MK VS , MK ĐANG CẦN RẤT...

NH

nguyễn hoàng lê thi

7 tháng 9 2016

#Toán lớp 7

1

PT

phan thị minh anh

7 tháng 9 2016

a.x+30/100x=-1,1

13/10x=-1,1

x=-11/13

b. (x-1/2):1/3 +5/7=9/5/7

(x-1/2):1/3=9

x-1/2=3

x=7/2

c. -5/6-x=7/12-1/3

x=-5/6-7/12-1/3

x=-7/4

d. 3(x+3)=-15

x+3=-5

x=-8

e. (4,5-2x)(-11/7)=11/14

4,5-2x=11/14:-11/7

4,5-2x=-1/2

2x=4,5+1/2

2x=5

x=5/2

AJ

agelina jolie

6 tháng 6 2016

tìm x biết...

3

PT

Phạm Tuấn Kiệt

6 tháng 6 2016

a) (x + 1/2) . (2/3 − 2x) = 0

\(\Rightarrow\left[\begin{array}{nghiempt}x+\frac{1}{2}=0\\\frac{2}{3}-2x=0\end{array}\right.\)

\(\Rightarrow\left[\begin{array}{nghiempt}x=-\frac{1}{2}\\2x=\frac{2}{3}\end{array}\right.\)

\(\Rightarrow\left[\begin{array}{nghiempt}x=-\frac{1}{2}\\x=\frac{1}{3}\end{array}\right.\)

b) \(\left(x.6\frac{2}{7}+\frac{3}{7}\right).2\frac{1}{5}-\frac{3}{7}=-2\)

\(\Rightarrow\left(x.\frac{44}{7}+\frac{3}{7}\right).\frac{11}{5}=-2+\frac{3}{7}\)

\(\Rightarrow\left(x.\frac{44}{7}+\frac{3}{7}\right).\frac{11}{5}=-\frac{11}{7}\)

\(\Rightarrow x.\frac{44}{7}+\frac{3}{7}=-\frac{11}{7}:\frac{11}{5}=-\frac{11}{7}.\frac{5}{11}\)

\(\Rightarrow x.\frac{44}{7}+\frac{3}{7}=-\frac{5}{7}\)

\(\Rightarrow x.\frac{44}{7}=-\frac{5}{7}-\frac{3}{7}\)

\(\Rightarrow x.\frac{44}{7}=-\frac{8}{7}\)

\(\Rightarrow x=-\frac{8}{7}:\frac{44}{7}=-\frac{8}{7}.\frac{7}{44}\)

\(\Rightarrow x=-\frac{2}{11}\)

PT

Phạm Tuấn Kiệt

6 tháng 6 2016

c) \(x.3\frac{1}{4}+\left(-\frac{7}{6}\right).x-1\frac{2}{3}=\frac{5}{12}\)

\(\Rightarrow x\left(3\frac{1}{4}-\frac{7}{6}\right)=\frac{5}{12}+\frac{5}{3}\)

\(\Rightarrow x\left(\frac{13}{4}-\frac{7}{6}\right)=\frac{25}{12}\)

\(\Rightarrow x.\frac{25}{12}=\frac{25}{12}\)

\(\Rightarrow x=\frac{25}{12}:\frac{25}{12}\)

\(\Rightarrow x=1\)

d) \(5\frac{8}{17}:x+\left(-\frac{4}{17}\right):x+3\frac{1}{7}:17\frac{1}{3}=\frac{4}{11}\)

\(\Rightarrow\left(5\frac{8}{17}-\frac{4}{17}\right):x+\frac{22}{7}:\frac{52}{3}=\frac{4}{11}\)

\(\Rightarrow5\frac{4}{17}:x+\frac{33}{182}=\frac{4}{11}\)

\(\Rightarrow\frac{89}{17}:x=\frac{4}{11}-\frac{33}{182}\)

\(\Rightarrow\frac{89}{17}:x=\frac{365}{2002}\)

\(\Rightarrow x=\frac{89}{17}:\frac{365}{2002}\)

\(\Rightarrow x\approx28,7\) (số hơi lẻ)

e) \(\frac{17}{2}-\left|2x-\frac{3}{4}\right|=-\frac{7}{4}\)

\(\Rightarrow\left|2x-\frac{3}{4}\right|=\frac{17}{2}+\frac{7}{4}\)

\(\Rightarrow\left|2x-\frac{3}{4}\right|=\frac{41}{4}\)

\(\Rightarrow\left[\begin{array}{nghiempt}2x-\frac{3}{4}=\frac{41}{4}\\2x-\frac{3}{4}=-\frac{41}{4}\end{array}\right.\)

\(\Rightarrow\left[\begin{array}{nghiempt}2x=11\\2x=-\frac{19}{2}\end{array}\right.\)

\(\Rightarrow\left[\begin{array}{nghiempt}x=\frac{11}{2}\\x=-\frac{19}{4}\end{array}\right.\)

\(\frac{4}{9}:\frac{-1}{7}+6\frac{5}{9}.\frac{2}{3}\)\(\left(\frac{-1}{3}\right)^4.\frac{4}{11}+\frac{7}{11}.\left(\frac{-1}{3}\right)^2\)\(\left(\frac{-1}{7}\right)^0-2\frac{4}{9}:\left(\frac{2}{3}\right)^2\)\(\left(\frac{1}{3}-\frac{5}{6}\right)^2+\frac{5}{6}:2\)Tìm x\(\left(\frac{3}{5}-\frac{1}{2}x\right)^2+8=12\)\(\frac{7}{12}-\left|\frac{1}{3}-\frac{1}{2}x\right|=\frac{1}{3}\)\(\frac{13}{12}-\frac{1}{3}.\left|\frac{1}{5}-\frac{1}{3}x\right|=\frac{1}{2}\)Nhanh hộ mình nhaCảm ơn...

CL

Chubby Lê

3 tháng 11 2018

Bài 1:tính nhanha. 6\(\frac{4}{5}\)-\(\left(1\frac{2}{3}+3\frac{4}{5}\right)\)b. \(7\frac{5}{9}-\left(2\frac{3}{4}+3\frac{5}{9}\right)\)c. \(\frac{-3}{5}.\frac{5}{7}+\frac{-3}{5}.\frac{3}{7}+\frac{-3}{5}.\frac{6}{7}\)d. \(\frac{1}{3}.\frac{4}{5}+\frac{1}{3}.\frac{6}{5}-\frac{4}{3}\)Bài 2: tìm xa. \(\frac{2}{3}+\frac{1}{3}:x=\frac{3}{5}\)b. \(x+30\%x=-1,3\)c. \(3\frac{1}{3}x+16\frac{3}{4}=-13,25\)d. \(\left(2\frac{4}{5}x-50\right):\frac{2}{3}=51\)e. |2x-1|=\(\left(-4\right)^2\)gấp nha các...

#Toán lớp 7

0

K

Kaijo

5 tháng 5 2020

1,Giải Pt

a,\(\frac{3x-7}{2}+\frac{x+1}{3}=-16\)

b,\(x-\frac{x+1}{3}=\frac{2x+1}{5}\)

c,\(\frac{7-3x}{12}+\frac{3}{4}=2\left(x-2\right)+\frac{5\left(5-2x\right)}{6}\)

e,\(\frac{3\left(x+3\right)}{4}+\frac{1}{2}=\frac{5x+9}{3}-\frac{7x-9}{4}\)

#Toán lớp 8

0

HL

Hỏa Long

9 tháng 4 2018

0

NB

Nguyễn Bảo Nhi

19 tháng 4 2019

...

8

NB

Nguyễn Bảo Nhi

19 tháng 4 2019

Câu a \(\left|2x-\frac{1}{3}\right|+\frac{5}{6}=1\)

KN

Kiệt Nguyễn

19 tháng 4 2019

g) \(\left(x+\frac{1}{2}\right)\left(\frac{2}{3}-2x\right)=0\)

\(\Leftrightarrow\orbr{\begin{cases}x+\frac{1}{2}=0\\\frac{2}{3}-2x=0\end{cases}}\Leftrightarrow\orbr{\begin{cases}x=\frac{-1}{2}\\x=\frac{1}{3}\end{cases}}\)

Vây \(x\in\left\{\frac{-1}{2};\frac{1}{3}\right\}\)