a. x³ = 8²

    x³ = 64

    x³ = 4³

    x   = 4

b. x²⁰ = x

x²⁰     = x²⁰

x        = 1

\(a,x^3=8^2\)

\(x^3=64\)

\(\Rightarrow x=4\)

\(b,x^{20}=x\)

\(\Rightarrow x^{20}-x=0\)

\(\Rightarrow x\left(x^{19}-1\right)=0\)

\(\Rightarrow\hept{\begin{cases}x=0\\x^{19}=1\Leftrightarrow x=1\end{cases}}\)

a, x^3=8^2 

   x^3=64

  x^3=4^3

  x=4

b,  x^20=x

     x^20-x=0

    x.(x^19-1)=0

\(\orbr{\begin{cases}x=0\\x^{19}-1=0\end{cases}}\)

\(\orbr{\begin{cases}x=0\\x^{19}=1\end{cases}}\)

\(\orbr{\begin{cases}x=0\\x=1\end{cases}}\)

                     Vậy          \(\orbr{\begin{cases}x=0\\x=1\end{cases}}\)(t/m)

b) (3.x - 24) . 7³ = 2 . 7⁴

(3.x - 24) . 343 = 4802

3.x - 24 = 4802 : 343

3.x - 24 = 14

3.x = 14 + 24

3.x = 38

Tự giải :))

c) x = 1 

a, 20 + 8.( x + 3 ) = 5^2 .4

20 + 8. ( x + 3 ) = 25 . 4

20 + 8. ( x + 3 ) = 100

        8. ( x + 3 ) = 100 - 20

        8 . ( x + 3 ) = 80

               x + 3 = 80 : 8

               x + 3 = 10

                    x = 10 - 3

                    x = 7

Vậy x = 7

b, /x+4/ - 12 = -6

/x+4/ = -6 + 12 

/x+4/ = 6

x+4 ∈ { 6 ; -6 }

x ∈ { 2 ; -2 }

Vậy x ∈ { 2 ; -2 }

#Học tốt#

sao lại "x,y" = -20

bn có vt sai đề k

????????????

a,5x+8=2x-7                         

5x+8-2x+7=0

<=>3x+15=0

<=>3x=-15

<=>x=-5

Vậy x=-5

   b,3.(x+2)=2.(x-1)

<=>3x+6=2x-1

<=>3x+6-2x+1=0

<=>x+7=0

<=>x=-7

Vậy x=-7

a,5x+8=2x-7

   5x - 2x = -7 - 8

    3x        = -15

      x        = (-15) : 3

      x        = -5

Vậy x = -5

 b,3.(x+2)=2.(x-1)

    3x + 6 = 2x - 2

    3x - 2x= -2 - 6

       x     = -8

Vậy x = -8

# HOK TỐT #

\(a,5x+8=2x-7\)

<=>\(5x-2x=\left(-7\right)-8\)

<=>\(3x=-15\)

<=>\(x=-5\)

\(b,3\left(x+2\right)=2\left(x-1\right)\)

<=>\(3x+6=2x-2\)

<=>\(3x-2x=\left(-2\right)-6\)

<=>\(x=-8\)

a) -12.(x - 5) + 7(3 - x) = 5

=> -12x + 60 + 21 - 7x = 5

=> -19x + 81 = 5

=> -19x = 5 - 81

=> -19x = -76

=> x = -76 : (-19)

=> x = 4

b) (x + 1) + (x + 2) + (x + 3) + ... + (x + 20) = 250

=> (x + x + x + ... + x) + (1 + 2 + 3 + ... + 20) = 250

=> 20x + 210 = 250

=> 20x = 250 - 210

=> 20x = 40

= > x = 40 : 20

=> x = 2

\(-12\left(x-5\right)+7\left(3-x\right)=5\)

\(\Leftrightarrow-12x+60+21-7x=5\)

\(\Leftrightarrow-19x+81=5\)

\(\Leftrightarrow81-5=19x\)

\(\Leftrightarrow19x=76\)

\(\Leftrightarrow x=4\)

\(\left(x+1\right)+\left(x+2\right)+\left(x+3\right)+...+\left(x+20\right)=250\)

\(\Leftrightarrow20x+\left(1+2+3+...+20\right)=250\)

\(\Leftrightarrow20x+\frac{20\left(20+1\right)}{2}=250\)

\(\Leftrightarrow20x+210=250\)

\(\Leftrightarrow20x=40\)

\(\Leftrightarrow x=2\)

\(\frac{2}{6}+\frac{2}{12}+...+\frac{2}{x\left(x+1\right):2}=\frac{2009}{2011}\)

\(2\left(\frac{1}{2.3}+\frac{1}{3.4}+...+\frac{1}{x\left(x+1\right)}\right)=\frac{2009}{2011}\)

\(2\left(\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+...+\frac{1}{x}-\frac{1}{x+1}\right)=\frac{2009}{2011}\)

\(2\left(\frac{1}{2}-\frac{1}{x+1}\right)=\frac{2009}{2011}\)

\(\frac{1}{2}-\frac{1}{x+1}=\frac{2009}{2011}:2\)

\(\frac{1}{2}-\frac{1}{x+1}=\frac{2009}{4022}\)

\(\frac{1}{x+1}=\frac{1}{2}-\frac{2009}{4022}\)

\(\frac{1}{x+1}=\frac{1}{2011}\)

=>x+1=2011

=>x=2010

`x-1/9 =8/3`

`=>x=8/3 +1/9`

`=> x= 24/9 +1/9`

`=>x= 25/9`

Vậy `x=25/9`

__

`x-2/20=-5/2-x`

`=>x+x=-5/2 +2/20`

`=> 2x= -50/20 +2/20`

`=> 2x= -48/20`

`=> x= -12/5:2`

`=>x=-12/5 xx1/2`

`=>x= -12/10`

`=>x= -6/5`

Vậy `x=-6/5`

`@` `\text {Ans}`

`\downarrow`

`a)`

Đề là \(\dfrac{x-1}{9}=\dfrac{8}{3}\) phải hongg bạn?

\(\dfrac{x-1}{9}=\dfrac{8}{3}\)

`=>` `(x-1)3 = 8*9`

`=> (x-1)3=72`

`=> x-1=72 \div 3`

`=> x-1=24`

`=> x=25`

`b)`

\(\dfrac{x-2}{20}=\dfrac{-5}{2-x}\)

`=>` `(x-2)(2-x)=20*(-5)`

`=> (x-2)(2-x)=-100`

`=> -[(x-2)(x-2)]=-100`

`=> -(x-2)^2 = -100`

`=> (x-2)^2 = 100`

`=> (x-2)^2 = (+-10)^2`

`=>`\(\left[{}\begin{matrix}x-2=10\\x-2=-10\end{matrix}\right.\)

`=>`\(\left[{}\begin{matrix}x=12\\x=-8\end{matrix}\right.\)