a: \(575-\left(2x+70\right)=445\)

=>\(2x+70=575-445=130\)

=>\(2x=130-70=60\)

=>x=60/2=30

b: \(575-2\left(x+70\right)=445\)

=>\(2\left(x+70\right)=575-445=130\)

=>x+70=130/2=65

=>x=65-70=-5

c: \(x^5=32\)

=>\(x^5=2^5\)

=>x=2

d: \(\left(3x-1\right)^3=8\)

=>\(\left(3x-1\right)^3=2^3\)

=>3x-1=2

=>3x=3

=>\(x=\dfrac{3}{3}=1\)

e: \(\left(x-2\right)^3=27\)

=>\(\left(x-2\right)^3=3^3\)

=>x-2=3

=>x=5

f: \(\left(2x-3\right)^2=9\)

=>\(\left[{}\begin{matrix}2x-3=3\\2x-3=-3\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}2x=6\\2x=0\end{matrix}\right.\)

=>\(\left[{}\begin{matrix}x=3\\x=0\end{matrix}\right.\)

g: \(2x+5=3^4:3^2\)

=>\(2x+5=3^2\)

=>2x+5=9

=>2x=9-5=4

=>x=4/2=2

h: \(\left(4x-5^2\right)\cdot7^3=7^4\)

=>\(4x-25=\dfrac{7^4}{7^3}=7\)

=>4x=25+7=32

=>\(x=\dfrac{32}{4}=8\)

a) => 6x-6-5x=15

=> 6x-6+6-5x=15+6

=> 6x-5x=21

=> x=21

b) => 8x-4-7x=16

=> 8x-4+4-7x=16+4

=> 8x-7x=20

=> x=20

c) => 8-[-(2.4x)]-9x-21=31

=> 8-(-8x)-9x=31+21

=> 8-(-8x)-9x=52

=> (-8x)-9x=8-52

=> (-8x)+(-9x)=-44

=> -17x=-44

=> x=(-44):(-17)

=> x=

câu c chắc tớ làm sai

a) x = 21

b) x = 20

c) x = -4

21

20

4

tic nha

gõ latex đi bn!

a. 2^x + 70 = 74

<=> 2^x = 4

<=> x = 2

b. 120 - \(\dfrac{4x}{2}\) = 80

<=> 120 - 2x = 80

<=> 120 - 80 = 2x

<=> 2x = 40

<=> x = 20

c. (3x + 5)² = 400

<=> \(|3x+5|=\sqrt{400}\)

<=> \(|3x+5|=20\)

<=> \(\left[{}\begin{matrix}3x+5=20\\3x+5=-20\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=5\\x=\dfrac{-25}{3}\end{matrix}\right.\) 

1) 3x-(4+2x)=11

    3x - 4 - 2x = 11

   3x - 2x = 11+4

     x = 15

Vậy x = 15.

2) 4x+5=11+2x

    4x - 2x = 11 - 5

    2x = 6

    x   = 6 : 2

     x  = 3

Vậy x  = 3.

3) 7x-17=31+x

    7x - x = 31  + 17

      6x = 48

        x = 48 : 6

       x  = 8

Vậy x = 8

# HOK TỐT #

\(3x-\left(4+2x\right)=11\)

\(3x-4-2x=11\)

\(x-15=0\)

\(x=15\)

\(4x+5=11+2x\)

\(2x-6=0\)

\(2x=6\)

\(x=3\)

Bn lm phần c đi , cố lên ! 

1) 3x-(4+2x)=11

    3x-4-2x=11

    3x-2x=11+4

          x=15

2) 4x+5=11+2x

    4x-2x=11-5

         2x=6

           x=6:2

           x=3

3) 7x-17=31+x

    7x-x=31+17

        6x=48

          x=48:6

          x=8

a,  70 - 5 ( x - 3 ) = 45

⇔ 5 . x - 3 = 70 - 45

⇔ 5 x - 3 = 35

⇔ x - 3 = 35 : 5 ⇔ x - 3 = 7

⇔ x = 10

b,  10 + 2 x = 4 5 : 4 3

⇔ 10 + 2 x = 4 2 ⇔ 10 + 2 x = 16

⇔ 2 x = 4 ⇔ x = 2

c,  60 - 3 x - 2 = 51

⇔ 3 x - 2 = 60 - 51

⇔ 3 x - 2 = 9

⇔ x - 2 = 3 ⇔ x = 5

d,  4 x - 20 = 2 5 : 2 3

⇔ 4 x - 20 = 2 2 ⇔ 4 x - 20 = 4

⇔ 4 x = 24 ⇔ x = 6

Ta có :\(15x=10y=6z\Rightarrow\hept{\begin{cases}15x=10y\\10y=6z\end{cases}}\Rightarrow\hept{\begin{cases}3x=2y\\5y=3z\end{cases}}\Rightarrow\hept{\begin{cases}\frac{x}{2}=\frac{y}{3}\\\frac{y}{3}=\frac{z}{5}\end{cases}}\Rightarrow\frac{x}{2}=\frac{y}{3}=\frac{z}{5}\)

Đặt \(\frac{x}{2}=\frac{y}{3}=\frac{z}{5}=k\Rightarrow\hept{\begin{cases}x=2k\\y=3k\\z=5k\end{cases}}\)

Khi đó 5x³ + 2y³ - z³ = 31

=> 5(2k)³ + 2(3k)³ - (5k)³ = 31

=> 40k³ + 54k³ - 125k³ = 31

=> -31k³ = 31

=> k³ = -1

=> k = -1

=> x = -2 ; y = -3 ; z = -5

b) Ta có 7x = 14y = 6z =>  \(\hept{\begin{cases}7x=14y\\14y=6z\end{cases}}\Rightarrow\hept{\begin{cases}x=2y\\7y=3z\end{cases}}\Rightarrow\hept{\begin{cases}\frac{x}{2}=\frac{y}{1}\\\frac{y}{3}=\frac{z}{7}\end{cases}}\Rightarrow\hept{\begin{cases}\frac{x}{6}=\frac{y}{3}\\\frac{y}{3}=\frac{z}{7}\end{cases}}\Rightarrow\frac{x}{6}=\frac{y}{3}=\frac{z}{7}\)

Đặt \(\frac{x}{6}=\frac{y}{3}=\frac{z}{7}=k\Rightarrow\hept{\begin{cases}x=6k\\y=3k\\z=7k\end{cases}}\)

Khi đó 2x² - 3y² = 5

<=> 2.(6k)² - 3.(3k)² = 5

=> 72k² - 27k² = 5

=> 45k² = 5

=> k² = 1/9

=> k = \(\pm\frac{1}{3}\)

Nếu k = 1/3 => x = 2 ; y = 1 ; z = 7/3

Nếu k = -1/3 => x = -2 ; y = - 1 ; z = -7/3

Vậy các cặp (x;y;z) thỏa mãn là : (2;1;7/3) ; (-2 ; - 1; -7/3)

c) Ta có : \(3x=8y=5z\Rightarrow\frac{3x}{120}=\frac{8y}{120}=\frac{5z}{120}\Rightarrow\frac{x}{40}=\frac{y}{15}=\frac{z}{24}\)

Đặt \(\frac{x}{40}=\frac{y}{15}=\frac{z}{24}=k\Rightarrow\hept{\begin{cases}x=40k\\y=15k\\z=24k\end{cases}}\)

Khi đó |x - 2y| = 5

<=> |40k - 2.15k| = 5

=>  |10k| = 5

=> \(\orbr{\begin{cases}10k=5\\10k=-5\end{cases}}\Rightarrow\orbr{\begin{cases}k=\frac{1}{2}\\k=-\frac{1}{2}\end{cases}}\)

Nếu k = 5 => x = 20 ; y = 7,5 ; z = 12

Nếu k = -5 => x = -20 ; y =-7,5 ; z = -12

d) 4x = 5y = 6z => \(\frac{4x}{60}=\frac{5y}{60}=\frac{6z}{60}\Rightarrow\frac{x}{15}=\frac{y}{12}=\frac{z}{10}\)

Đặt \(\frac{x}{15}=\frac{y}{12}=\frac{z}{10}=k\Rightarrow\hept{\begin{cases}x=15k\\y=12k\\z=10k\end{cases}}\)

Khi đó (3x - 2y)² = 16

<=> (3.15k - 2.12k)² = 16

=> (45k -24k)² = 16

=> (21k)² = 16

=> \(\orbr{\begin{cases}21k=4\\21k=-4\end{cases}}\Rightarrow\orbr{\begin{cases}k=\frac{4}{21}\\k=-\frac{4}{21}\end{cases}}\)

Nếu k = 4/21 => x = 20/7 ; y = 16/7 ; z = 40/21

Nếu k = -4/21 => x = -20/7 ; y = -16/7 ; z = -40/21

Ai có cách làm khác không