Câu 1: Tìm x biết a) $-\dfrac{2}{3}$$\left(x-\dfrac{1}{4}\right)$ = $\dfrac{1}{3}\left(2x-1\right)$ b) $\dfrac{1}{5}.2^x \dfrac{1}{3}.2^{x 1}=\dfrac{1}{5}.2^7 \dfrac{1}{3}.2^8$ Câu 2: a) Ch...

4

PT

Phan Thanh Bình

7 tháng 4 2017

Câu 1:

a) $-\dfrac{2}{3}\left(x-\dfrac{1}{4}\right)=\dfrac{1}{3}\left(2x-1\right)$

$\Rightarrow-\dfrac{2}{3x}+\dfrac{1}{6}=\dfrac{2}{3}x-\dfrac{1}{3}$

$\Rightarrow\dfrac{2}{3}x+\dfrac{2}{3}x=\dfrac{1}{6}+\dfrac{1}{3}$

$\Rightarrow x.\left(\dfrac{2}{3}+\dfrac{2}{3}\right)=\dfrac{1}{2}$

$\Rightarrow x.\dfrac{4}{3}=\dfrac{1}{2}$

$\Rightarrow x=\dfrac{1}{2}:\dfrac{4}{3}$

$\Rightarrow x=\dfrac{3}{8}$

HH

Hoàng Hà Nhi

7 tháng 4 2017

lấy bài bd

KJ

❖ Khang/GD❄ 『ʈєɑɱ❖Hoàng๖ۣۜGia☆』

29 tháng 1 2022

Tìm x...

2

KS

Kudo Shinichi AKIRA^_^

29 tháng 1 2022

Chia nhỏ ra

NL

Nguyễn Lê Phước Thịnh

29 tháng 1 2022

a: =>1/2x=7/2-2/3=21/6-4/6=17/6

=>x=17/3

b: =>2/3:x=-7-1/3=-22/3

=>x=2/3:(-22/3)=-1/11

c: =>1/3x+2/5x-2/5=0

=>11/15x=2/5

hay x=6/11

d: =>2x-3=0 hoặc 6-2x=0

=>x=3/2 hoặc x=3

câu 1 $\dfrac{3\left(2x+1\right)}{4}$-$\dfrac{2\left(3x-1\right)}{5}$=5câu 2 $\dfrac{5x-3}{6}$+5-$\dfrac{7x-1}{4}$=$\dfrac{x+2}{12}$câu 3 $\dfrac{\left(x-1\right)\left(x+1\right)}{2}$+$\dfrac{3\left(x+1\right)}{4}$=$\dfrac{\left(x-2\right)^2}{2}$câu 4 $\dfrac{\left(x-4\right)^3}{6}$+1=$\dfrac{x\left(x+1\right)}{2}$-$\dfrac{\left(x-5\right)\left(x+5\right)}{3}$câu...

SP

Sửu Phạm

20 tháng 1 2022

#Toán lớp 8

2

NL

Nguyễn Lê Phước Thịnh

20 tháng 1 2022

Câu 1:

=>15(2x+1)-8(3x-1)=100

=>30x+15-24x+8=100

=>6x+23=100

hay x=77/6

Câu 2:

=>2(5x-3)+12-3(7x-1)=x+2

=>10x-6+12-21x+3-x-2=0

=>-12x=-7

hay x=7/12

Câu 3:

$\Leftrightarrow2\left(x^2-1\right)+3\left(x+1\right)=2\left(x^2-4x+4\right)$

$\Leftrightarrow2x^2-2+3x+3-2x^2+8x-8=0$

=>11x-7=0

hay x=-7/11

HL

Hồ Lê Thiên Đức

20 tháng 1 2022

Câu 4:

(x - 4)^3/6 + 1 = x(x + 1)/2 - (x - 5)(x + 5)/3

<=> (x - 4)^3 + 6/6 = x^2 + x/2 - x^2 - 25/3

<=> (x - 4)^3 + 6/6 = 3x^2 + 3x - 2x^2 + 50/6

<=> (x - 4)^3 + 6 = 3x^2 + 3x - 2x^2 + 50

<=> x^3 - 12x^2 + 48x - 58 = x^2 + 3x + 50

<=> x^3 -13x^2 + 45x - 108 = 0

Đến đây bạn bấm máy nhẩm nghiệm là ra nhé

Câu 5:

3(x + 2)^3/5 - (x - 1)^2/10 = (x - 3)(x + 3)/2

<=> 6(x + 2)^3 - (x - 1)^2/10 = 5(x^2 - 9)/10

<=> 6(x + 2)^3 - (x - 1)^2 = 5(x^2 - 9)

<=> 6x^3 + 36x^2 + 72x + 48 - x^2 + 2x - 1 - 5x^2 + 45 = 0

<=> 6x^3 + 30x^2 + 74x + 92 = 0

Đến đây bạn bấm máy nhẩm nghiệm như câu 4 nhé

TL

Trần Linh

4 tháng 5 2022

Câu 1: Thực hiện phép tính

a, $40\dfrac{1}{4}:\dfrac{5}{7}-25\dfrac{1}{4}:\dfrac{5}{7}-\dfrac{1}{2021}$

b, $\left|\dfrac{-5}{9}\right|.\sqrt{81}-2021^0.\dfrac{16}{25}$

Câu 2: Tìm x

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

1

NL

Nguyễn Lê Phước Thịnh

17 tháng 6 2023

1:

a: =7/5(40+1/4-25-1/4)-1/2021

=21-1/2021=42440/2021

b: =5/9*9-1*16/25=5-16/25=109/25

KJ

❖ Khang/GD❄ 『ʈєɑɱ❖Hoàng๖ۣۜGia☆』

28 tháng 2 2022

Tìm x biết:

$a,\left(x-\dfrac{3}{4}\right)+50\%=\dfrac{1}{6}$

$b,\dfrac{1}{2}x-\dfrac{5}{6}x=\dfrac{7}{2}$

$c,\left(4-x\right)\left(3x+5\right)=0$

$d,\dfrac{x}{16}=\dfrac{50}{32}$

$e,\left(2x-3\right)+\dfrac{3}{2}=-\dfrac{1}{4}$

1

NL

Nguyễn Lê Phước Thịnh

28 tháng 2 2022

a: =>x-3/4=1/6-1/2=1/6-3/6=-2/6=-1/3

=>x=-1/3+3/4=-4/12+9/12=5/12

b: =>x(1/2-5/6)=7/2

=>-1/3x=7/2

hay x=-21/2

c: (4-x)(3x+5)=0

=>4-x=0 hoặc 3x+5=0

=>x=4 hoặc x=-5/3

d: x/16=50/32

=>x/16=25/16

hay x=25

e: =>2x-3=-1/4-3/2=-1/4-6/4=-7/4

=>2x=-7/4+3=5/4

hay x=5/8

1. $\dfrac{5\left(x-1\right)+2}{6}-\dfrac{7x-1}{4}=\dfrac{2\left(2x+1\right)}{7}-5$ 2. $x-\dfrac{3\left(x+30\right)}{15}-24\dfrac{1}{2}=\dfrac{7x}{10}-\dfrac{2\left(10x+2\right)}{5}$ 3. $14\dfrac{1}{2}-\dfrac{2\left(x+3\right)}{5}=\dfrac{3x}{2}-\dfrac{2\left(x-7\right)}{3}$ 4. $\dfrac{x+1}{3}+\dfrac{3\left(2x+1\right)}{4}=\dfrac{2x+3\left(x+1\right)}{6}+\dfrac{7+12x}{12}$ 5. $\dfrac{3\left(2x-1\right)}{4}-\dfrac{3x+1}{10}+1=\dfrac{2\left(3x+2\right)}{5}$ 6....

WH

원회으Won Hoe Eu

13 tháng 2 2019

#Toán lớp 8

0

TD

Thầy Đức Anh

Giáo viên VIP

27 tháng 4 2022

Tìm $x$, biết :
a) $\left(\dfrac{1}{2}+1,5\right) \cdot x=\dfrac{1}{5}$
b) $\left(-1 \dfrac{3}{5}+x\right): \dfrac{12}{13}=2 \dfrac{1}{6}$
c) $\left(x: 2 \dfrac{1}{3}\right) \cdot \dfrac{1}{7}=\dfrac{-3}{8}$
d) $\dfrac{-4}{7} \cdot x+\dfrac{7}{5}=\dfrac{1}{8}:\left(-1 \dfrac{2}{3}\right)$

13

YN

Yen Nhi

21 tháng 6 2022

$a)\left(\dfrac{1}{2}+1,5\right)x=\dfrac{1}{5}$

$\Rightarrow2x=\dfrac{1}{5}$

$\Rightarrow x=\dfrac{1}{10}$

$b)\left(-1\dfrac{3}{5}+x\right):\dfrac{12}{13}=2\dfrac{1}{6}$

$\Leftrightarrow-\dfrac{8}{5}+x=\dfrac{13}{6}.\dfrac{12}{13}$

$\Leftrightarrow-\dfrac{8}{5}+x=2$

$\Leftrightarrow x=\dfrac{18}{5}$

$c)\left(x:2\dfrac{1}{3}\right).\dfrac{1}{7}=-\dfrac{3}{8}$

$\Leftrightarrow x:\dfrac{7}{3}=-\dfrac{3}{8}:\dfrac{1}{7}$

$\Leftrightarrow x=-\dfrac{21}{8}.\dfrac{7}{3}$

$\Leftrightarrow x=-\dfrac{49}{8}$

$d)-\dfrac{4}{7}x+\dfrac{7}{5}=\dfrac{1}{8}:\left(-1\dfrac{2}{3}\right)$

$\Leftrightarrow-\dfrac{4}{7}x+\dfrac{7}{5}=-\dfrac{3}{40}$

$\Leftrightarrow-\dfrac{4}{7}x=-\dfrac{59}{40}$

$\Leftrightarrow x=\dfrac{413}{160}$

T

TINH

13 tháng 7 2022

a) $\left(\dfrac{1}{2}+1,5\right) \cdot x=\dfrac{1}{5}$

$\cdot x=\dfrac{1}{5}$

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

$x=\dfrac{1}{10}$
b) $\left(-1 \dfrac{3}{5}+x\right): \dfrac{12}{13}=2 \dfrac{1}{6}$

$\dfrac{3}{5}+x=\dfrac{13}{6} \cdot \dfrac{12}{13}$
$\dfrac{3}{5}$

$\dfrac{3}{5}$
c) $\left(x: 2 \dfrac{1}{3}\right) \cdot \dfrac{1}{7}=\dfrac{-3}{8}$

$\cdot \dfrac{3}{7} \cdot \dfrac{1}{7}=\dfrac{-3}{8}$

$x=\dfrac{-3}{8}: \dfrac{3}{49}$
$x=\dfrac{-49}{8}=-6 \dfrac{1}{8}$
d) $\dfrac{-4}{7} \cdot x+\dfrac{7}{5}=\dfrac{1}{8}:\left(-1 \dfrac{2}{3}\right)$

$\dfrac{-4}{7} x+\dfrac{7}{5}=\dfrac{1}{8} \cdot \dfrac{-3}{5}$
$-\dfrac{4}{7} x=\dfrac{-3}{40}-\dfrac{7}{5} \\ x=\dfrac{-59}{40}: \dfrac{-4}{7}=\dfrac{413}{160}=2 \dfrac{93}{160}$

KJ

❖ Khang/GD❄ 『ʈєɑɱ❖Hoàng๖ۣۜGia☆』

22 tháng 2 2022

Tìm x, biết:

$a,\dfrac{1}{3}:\left(2x-1\right)=\dfrac{-1}{6}$

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

$c,\dfrac{x}{8}=\dfrac{9}{4}$

$d,\dfrac{x-3}{2}=\dfrac{18}{x-3}$

$e,4,5x-6,2x=6,12$

$h,11,4-\left(x-3,4\right)=-16,2$

2

NL

Nguyễn Lê Phước Thịnh

22 tháng 2 2022

a: =>2x-1=-2

=>2x=-1

hay x=-1/2

b: $\Leftrightarrow\left[{}\begin{matrix}3x+2=0\\-\dfrac{2}{5}x-7=0\end{matrix}\right.\Leftrightarrow x\in\left\{-\dfrac{2}{3};-\dfrac{35}{2}\right\}$

c: x/8=9/4

nên x/8=18/8

hay x=18

d: $\Leftrightarrow\left(x-3\right)^2=36$

=>x-3=6 hoặc x-3=-6

=>x=9 hoặc x=-3

e: =>-1,7x=6,12

hay x=-3,6

h: =>x-3,4=27,6

hay x=31

R

Rhider

22 tháng 2 2022

a) $\dfrac{1}{3}\div\left(2x-1\right)=\dfrac{-1}{6}$

$\left(2x-1\right).\dfrac{1}{3}\div\left(2x-1\right)=\left(2x-1\right)\left(-\dfrac{1}{6}\right)$

$\dfrac{1}{3}=\left(2x-1\right)\left(-\dfrac{1}{6}\right)$

$\dfrac{1}{3}=-1\left(2x-1\right)\div6$

$\dfrac{1}{3}=-2x+1\div6$

$x=-\dfrac{1}{2}$

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

$TH1:3x+2=0$

$3x=0-2$

$3x=-2$

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

$TH2:\left(-\dfrac{2}{5}x-7\right)=0$

$\left(\dfrac{-2}{5}x-7\right)=0$

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

$\left(\dfrac{-2x-35}{5}\right)=0$

$-2x-35=0$

$-2x=0+35$

$x=-\dfrac{35}{2}$

c) $\dfrac{x}{8}=\dfrac{9}{4}$

$\Leftrightarrow x=\dfrac{9.8}{4}=\dfrac{72}{4}=18$

$x=18$

d) $\dfrac{x-3}{2}=\dfrac{18}{x-3}$

$x-3=18+2$

$x=20-3$

$x=17$

e) $4,5x-6,2x=6,12$

$\dfrac{9x}{2}-6,2.x=6,12$

$\dfrac{9x}{2}+\dfrac{-31x}{5}=6,12$

$\dfrac{5.9x}{10}+\dfrac{2\left(-31\right)x}{10}=6.12$

$\dfrac{45x-62x}{10}=6.12$

$=-17x\div10=6.12$

$-17x=10.6.12$

$x=-3,6$

h) $11,4-\left(x-3,4\right)=-16,2$

$x-3,4=-16,2+11,4$

$x-3,4=-4,8$

$x=-1,4$

Đúng(2)

NT

Nguyễn Thu Huyền

1 tháng 9 2023

Tìm...

Cần giúp nhanh vsBài 1. Tìm xa) $\left|x+\dfrac{7}{4}\right|=\dfrac{1}{2}$b) $\left|2x+1\right|-\dfrac{2}{5}=\dfrac{1}{3}$c) $3x.\left(x+\dfrac{2}{3}\right)=0$d) $x+\dfrac{1}{3}=\dfrac{2}{5}-\left(-\dfrac{1}{3}\right)$Bài 2. Tính...

3

T

Toru

1 tháng 9 2023

$a,3-x=x+1,8$

$\Rightarrow-x-x=1,8-3$

$\Rightarrow-2x=-1,2$

$\Rightarrow x=0,6$

$b,2x-5=7x+35$

$\Rightarrow2x-7x=35+5$

$\Rightarrow-5x=40$

$\Rightarrow x=-8$

$c,2\left(x+10\right)=3\left(x-6\right)$

$\Rightarrow2x+20=3x-18$

$\Rightarrow2x-3x=-18-20$

$\Rightarrow-x=-38$

$\Rightarrow x=38$

$d,8\left(x-\dfrac{3}{8}\right)+1=6\left(\dfrac{1}{6}+x\right)+x$

$\Rightarrow8x-3+1=1+6x+x$

$\Rightarrow8x-3=7x$

$\Rightarrow8x-7x=3$

$\Rightarrow x=3$

$e,\dfrac{2}{9}-3x=\dfrac{4}{3}-x$

$\Rightarrow-3x+x=\dfrac{4}{3}-\dfrac{2}{9}$

$\Rightarrow-2x=\dfrac{10}{9}$

$\Rightarrow x=-\dfrac{5}{9}$

Đúng(3)

T

Toru

1 tháng 9 2023

$g,\dfrac{1}{2}x+\dfrac{5}{6}=\dfrac{3}{4}x-\dfrac{1}{2}$

$\Rightarrow\dfrac{1}{2}x-\dfrac{3}{4}x=-\dfrac{1}{2}-\dfrac{5}{6}$

$\Rightarrow-\dfrac{1}{4}x=-\dfrac{4}{3}$

$\Rightarrow x=\dfrac{16}{3}$

$h,x-4=\dfrac{5}{6}\left(6-\dfrac{6}{5}x\right)$

$\Rightarrow x-4=5-x$

$\Rightarrow x+x=5+4$

$\Rightarrow2x=9$

$\Rightarrow x=\dfrac{9}{2}$

$k,7x^2-11=6x^2-2$

$\Rightarrow7x^2-6x^2=-2+11$

$\Rightarrow x^2=9\Rightarrow\left[{}\begin{matrix}x=3\\x=-3\end{matrix}\right.$

$m,5\left(x+3\cdot2^3\right)=10^2$

$\Rightarrow5\left(x+24\right)=100$

$\Rightarrow x+24=20$

$\Rightarrow x=-4$

$n,\dfrac{4}{9}-\left(\dfrac{1}{6^2}\right)=\dfrac{2}{3}\left(x-\dfrac{2}{3}\right)^2+\dfrac{5}{12}$

$\Rightarrow\dfrac{2}{3}\left(x-\dfrac{2}{3}\right)^2+\dfrac{5}{12}=\dfrac{4}{9}-\dfrac{1}{36}$

$\Rightarrow\dfrac{2}{3}\left(x-\dfrac{2}{3}\right)^2+\dfrac{5}{12}=\dfrac{5}{12}$

$\Rightarrow\dfrac{2}{3}\left(x-\dfrac{2}{3}\right)^2=0$

$\Rightarrow x-\dfrac{2}{3}=0\Rightarrow x=\dfrac{2}{3}$

#$Urushi\text{☕}$

Đúng(3)

NQ

Nguyễn Quý Trung

25 tháng 7 2021

5

AH

Akai Haruma

Giáo viên

25 tháng 7 2021

Bài 1:

a.

$|x+\frac{7}{4}|=\frac{1}{2}$

$\Leftrightarrow \left[\begin{matrix} x+\frac{7}{4}=\frac{1}{2}\\ x+\frac{7}{4}=-\frac{1}{2}\end{matrix}\right.\Leftrightarrow \left[\begin{matrix} x=\frac{-5}{4}\\ x=\frac{-9}{4}\end{matrix}\right.$

b. $|2x+1|-\frac{2}{5}=\frac{1}{3}$
$|2x+1|=\frac{1}{3}+\frac{2}{5}$

$|2x+1|=\frac{11}{15}$

$\Leftrightarrow \left[\begin{matrix} 2x+1=\frac{11}{15}\\ 2x+1=\frac{-11}{15}\end{matrix}\right.\Leftrightarrow \left[\begin{matrix} x=\frac{-2}{15}\\ x=\frac{-13}{15}\end{matrix}\right.$

c.

$3x(x+\frac{2}{3})=0$

$\Leftrightarrow \left[\begin{matrix} 3x=0\\ x+\frac{2}{3}=0\end{matrix}\right.\Leftrightarrow \left[\begin{matrix} x=0\\ x=\frac{-3}{2}\end{matrix}\right.$

d.

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

$\Leftrightarrow x=\frac{2}{5}$

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AH

Akai Haruma

Giáo viên

25 tháng 7 2021

Nguyễn Quý Trung:

$x+\dfrac{1}{3}=\dfrac{2}{5}+\dfrac{1}{3}$

Bạn bớt 2 vế đi 1/3 thì $x=\dfrac{2}{5}$

Đúng(2)

HQ

Hạ Quỳnh

20 tháng 12 2020

Bài 2:Tìm x...

1

NL

Nguyễn Lê Phước Thịnh

20 tháng 12 2020

a) Ta có: $\dfrac{1}{7}+x=-\dfrac{2}{3}$

$\Leftrightarrow x=-\dfrac{2}{3}-\dfrac{1}{7}=\dfrac{-14}{21}-\dfrac{3}{21}$

hay $x=-\dfrac{17}{21}$

Vậy: $x=-\dfrac{17}{21}$

b) Ta có: $\dfrac{-2}{3}:x=\dfrac{-5}{6}$

$\Leftrightarrow x=\dfrac{-2}{3}:\dfrac{-5}{6}=\dfrac{-2}{3}\cdot\dfrac{6}{-5}=\dfrac{-12}{-15}=\dfrac{4}{5}$

Vậy: $x=\dfrac{4}{5}$

c) Ta có: $\left(\dfrac{3}{5}-2x\right)\cdot\dfrac{5}{8}=1$

$\Leftrightarrow\left(\dfrac{3}{5}-2x\right)=1:\dfrac{5}{8}=\dfrac{8}{5}$

$\Leftrightarrow-2x=\dfrac{8}{5}-\dfrac{3}{5}=1$

hay $x=-\dfrac{1}{2}$

Vậy: $x=-\dfrac{1}{2}$

d) Ta có: $\dfrac{3}{4}+\dfrac{2}{5}x=\dfrac{29}{60}$

$\Leftrightarrow x\cdot\dfrac{2}{5}=\dfrac{29}{60}-\dfrac{3}{4}=\dfrac{29}{60}-\dfrac{45}{60}=\dfrac{-16}{60}=\dfrac{-4}{15}$

hay $x=\dfrac{-4}{15}:\dfrac{2}{5}=\dfrac{-4}{15}\cdot\dfrac{5}{2}=\dfrac{-20}{30}=-\dfrac{2}{3}$

Vậy: $x=-\dfrac{2}{3}$

e) Ta có: $\dfrac{3}{4}+\dfrac{1}{4}:x=\dfrac{2}{5}$

$\Leftrightarrow\dfrac{1}{4}:x=\dfrac{2}{5}-\dfrac{3}{4}=\dfrac{8}{20}-\dfrac{15}{20}=\dfrac{-7}{20}$

hay $x=-\dfrac{1}{4}:\dfrac{7}{20}=\dfrac{-1}{4}\cdot\dfrac{20}{7}=\dfrac{-20}{28}=\dfrac{-5}{7}$

Vậy: $x=-\dfrac{5}{7}$

f) Ta có: $\dfrac{11}{12}-\left(\dfrac{2}{5}+x\right)=\dfrac{2}{3}$

$\Leftrightarrow-x+\dfrac{11}{12}-\dfrac{2}{5}-\dfrac{2}{3}=0$

$\Leftrightarrow-x+\dfrac{55}{60}-\dfrac{24}{60}-\dfrac{40}{60}=0$

$\Leftrightarrow-x-\dfrac{9}{60}=0$

$\Leftrightarrow-x=\dfrac{9}{60}=\dfrac{3}{20}$

hay $x=-\dfrac{3}{20}$

Vậy: $x=-\dfrac{3}{20}$

g) Ta có: $\left|x+\dfrac{1}{3}\right|-4=\dfrac{-1}{2}$

$\Leftrightarrow\left|x+\dfrac{1}{3}\right|=\dfrac{-1}{2}+4=\dfrac{-1}{2}+\dfrac{8}{2}=\dfrac{7}{2}$

$\Leftrightarrow\left[{}\begin{matrix}x+\dfrac{1}{3}=\dfrac{7}{2}\\x+\dfrac{1}{3}=-\dfrac{7}{2}\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=\dfrac{7}{2}-\dfrac{1}{3}=\dfrac{21}{6}-\dfrac{2}{6}=\dfrac{19}{6}\\x=-\dfrac{7}{2}-\dfrac{1}{3}=\dfrac{-21}{6}-\dfrac{2}{6}=\dfrac{-23}{6}\end{matrix}\right.$

Vậy: $x\in\left\{\dfrac{19}{6};-\dfrac{23}{6}\right\}$

HQ

Hạ Quỳnh

20 tháng 12 2020

cảm ơn cậu cutee gì đó ơi nha