a)(2x+4).8-40=24

(2x+4).8=24+40

(2x+4).8=64

2x+4=64:8

2x+4=8

2x=8+4

2x=12

x=12:2

x=6

b)(2x+4²)-8=64:2

(2x+16)-8=32

2x+16=32+8

2x+16=40

2x=40-16

2x=24

x=24:2

x=12

c)(3x+2).4-20=24

(3x+2).4=24+20

(3x+2).4=44

3x+2=44:4

3x+2=11

3x=11-2

3x=9

x=9:3

x=3

\(-4\left(x-10\right)+5=-2x-\left(x+7\right)-\left(-20+8\right)\)

\(\Leftrightarrow-4x+40+5=-2x-x-7+20-8\)

\(\Leftrightarrow-4x+2x+x=-40-5-7-20-8\)

\(\Leftrightarrow-x=-80\)

\(\Leftrightarrow x=80\)

Vậy...

Bài 1:

a. $(-20)+x=-30$

$x-20=-30$

$x=-30+20=-(30-20)=-10$

b.

$(-10)-x=-20$

$x=(-10)-(-20)=-10+20=20-10=10$

c. Đề sai. Bạn xem lại.

d.

$x+(-3)=-7$

$x=-7-(-3)=-7+3=-(7-3)=-4$

e.

$x-(-5)=-9$

$x=(-9)+(-5)=-14$

f.

$x(-11)=12$

$x=\frac{12}{-11}=\frac{-12}{11}$

h.

$2x-10=20$

$2x=20+10=30$

$x=30:2=15$

l.

$4x-8=-8$
$4x=-8+8=0$

$x=0:4=0$

k.

$-12-(-2)x=-8$

$(-2)x=-12-(-8)=-12+8=-(12-8)=-4$

$x=(-4):(-2)=2$

Bài 2:

a. $-20-(10-x)=-3$

$10-x=-20-(-3)=-20+3=-(20-3)=-17$

$x=10-(-17)=10+17=27$

b.

$14+(14-x)=-2$
$14-x=-2-14=-16$

$x=14-(-16)=14+16=30$

c.

$-15-(x-3)=-7$

$x-3=-15-(-7)=-15+7=-8$

x=-8+3=-5$

d.

$(x+4)+(-20)=-8$

$x+4=-8-(-20)=-8+20=12$
$x=12-4=8$

e.

$-2x-2=-4$

$-2x=-4+2=-2$

$x=(-2):(-2)=1$

f.

$-2x+4=-4$

$-2x=-4-4=-8$

$x=(-8):(-2)=4$

l.

$-12-(-2)x=-2-4=-6$

$(-2)x=-12-(-6)=-12+6=-6$

$x=(-6):(-2)=3$

a,\(\left(\frac{7}{5}-2x\right).\frac{40}{20}=\frac{8}{14}\)

\(\Rightarrow\left(\frac{7}{5}-2x\right).2=\frac{4}{7}\)

\(\Rightarrow\frac{7}{5}-2x=\frac{4}{7}:2\)

\(\Rightarrow\frac{7}{5}-2x=\frac{2}{7}\)

\(\Rightarrow2x=\frac{7}{5}-\frac{2}{7}\)

\(\Rightarrow2x=\frac{39}{35}\)

\(\Rightarrow x=\frac{39}{35}:2\)

\(\Rightarrow x=\frac{39}{70}\)

b, \(\frac{7}{2}.x-20\%.x=-4\)

\(\Rightarrow x\left(\frac{7}{2}-20\%\right)=-4\)

\(\Rightarrow x\left(\frac{7}{2}-\frac{1}{5}\right)=-4\)

\(\Rightarrow x\frac{7}{10}=-4\)

\(\Rightarrow x=-4:\frac{7}{10}\)

\(\Rightarrow x=-\frac{40}{7}\)

(2x+1)^4=(2x+1)^6

vay 2x+1=0hoac1

vay x=0 hoac x=-1/2

b: \(\Leftrightarrow\dfrac{20}{x}-\dfrac{20}{x+20}=\dfrac{1}{6}\)

=>\(\dfrac{20x+400-20x}{x\left(x+20\right)}=\dfrac{1}{6}\)

=>x*(x+20)=400*6=2400

=>x^2+20x-2400=0

=>(x+60)(x-40)=0

=>x=-60 hoặc x=40

c: \(\dfrac{2x+1}{2x-1}-\dfrac{2x-1}{2x+1}=\dfrac{8}{4x^2-1}\)

=>(2x+1)^2-(2x-1)^2=8

=>4x^2+4x+1-4x^2+4x-1=8

=>8x=8

=>x=1(nhận)

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

\(\Rightarrow3x+\frac{3}{2}=x\)

\(\Rightarrow x-3x=\frac{3}{2}\)

\(\Rightarrow-2x=\frac{3}{2}\)

\(\Rightarrow x=\frac{3}{2}:-2\)

\(\Rightarrow x=\frac{3}{2}.-\frac{1}{2}\)

\(\Rightarrow x=-\frac{3}{4}\)

Vậy \(x=-\frac{3}{4}\)

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

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

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

\(\Rightarrow6x=2x-3\)

\(6x-2x=3\)

\(4x=3\)

\(x=\frac{3}{4}\)

\(\frac{1-2x}{9}=\frac{1}{1-2x}\)

\(\Rightarrow\left(1-2x\right).\left(1-2x\right)=1.9\)

\(\Rightarrow\left(1-2x\right)^2=\left(\pm3\right)^2\)

\(\Rightarrow\orbr{\begin{cases}1-2x=3\\1-2x=-3\end{cases}\Leftrightarrow\orbr{\begin{cases}2x=-2\\2x=4\end{cases}\Leftrightarrow}\orbr{\begin{cases}x=-1\\x=2\end{cases}}}\)

\(\frac{4}{5}=\frac{12}{x}=\frac{y}{20}=\frac{8.\left(y-x\right)}{z}\)

\(\Rightarrow\frac{4}{5}=\frac{12}{x}\)

\(4x=60\)

\(x=15\)

\(\frac{4}{5}=\frac{y}{20}\)

\(y5=80\)

\(y=16\)

\(\frac{4}{5}=\frac{8\left(y-x\right)}{z}\Leftrightarrow\frac{4}{5}=\frac{8.\left(80-15\right)}{z}\Leftrightarrow\frac{4}{5}=\frac{520}{z}\)

\(\Leftrightarrow4z=2600\)

\(z=650\)

Vậy ... ( bạn tự kết luận nhé )

chúc bạn học tốt !!!

1, \(\frac{x+1}{2}=\frac{x}{3}\)

<=> 3(x+1)=2x

<=> 3x+3-2x=0

<=> x+3=0

<=> x=-3

2, \(\frac{1-2x}{9}=\frac{1}{1-2x}\left(x\ne\frac{1}{2}\right)\)

<=> (1-2x)²=9

<=> \(\orbr{\begin{cases}1-2x=3\\1-2x=-3\end{cases}\Leftrightarrow\orbr{\begin{cases}2x=-2\\2x=4\end{cases}\Leftrightarrow}\orbr{\begin{cases}x=-1\\x=2\end{cases}}\left(tmđk\right)}\)

Vậy x={-1;2}