Ta có :\(\frac{x-1}{12}=\frac{25}{x-1}\)\(\Rightarrow\left(x-1\right)\left(x-1\right)=12.25\)

                                          \(\Rightarrow\left(x-1\right)^2=300\)

                                          \(\Rightarrow x\in\varnothing\)

\(\frac{x-1}{12}=\frac{25}{x-1}\)

\(\Rightarrow\left(x-1\right)^2=300\)

\(\Rightarrow\left(x-1\right)^2-(10\sqrt{3})^2=0\)

\(\Rightarrow(x-1-10\sqrt{3})\left(x-1+10\sqrt{3}\right)=0\)

\(\Rightarrow\hept{\begin{cases}x=1+10\sqrt{3}\\x=1-10\sqrt{3}\end{cases}}\)

x - 1/12 = 25/x - 1

<=> (x - 1).(x - 1) = 12.25

<=> (x - 1)² = 300

=> không có x thỏa mãn đề bài

a) \(11-\left(15-21\right)=x-\left(25-9\right)\)

\(\Leftrightarrow11-15+21+25-9=x\)

\(\Leftrightarrow x=33\)

b) \(2-x=17-\left(-5\right)\)

\(\Leftrightarrow2-x=22\)

\(\Leftrightarrow x=-20\)

c) \(x-12=\left(-9\right)-15\)

\(\Leftrightarrow x-12=-24\)

\(\Leftrightarrow x=-12\)

d) \(9-25=\left(7-x\right)-\left(25+7\right)\)

\(\Leftrightarrow-16=7-x-25-7\)

\(\Leftrightarrow x=-9\)

a) 11-(15+21)=x-(25-9)     

    11-36=x-25+9

    -25=x-(25+9)

    -25=x-34

       x=-25+34

       x=9

Vậy x=9      

b) 2-x=17-(-5)

    2-x=22

       x=2-22

       x=-20

Vậy x=-20

c) x-12=(-9)-15

    x-12=-24

         x=-24+12

         x=-12

Vậy x=-12            

d) 9-25=(7-x)-(25+7)

    16=7-x-32

    48=7-x

      x=-41

Vậy x=-41

Trả lời:

\(a,\)\(11-\left(15+21\right)=x-\left(25-9\right)\)

\(\Leftrightarrow11-36=x-16\)

\(\Leftrightarrow x-16=-25\)

\(\Leftrightarrow x=-9\)(Thỏa mãn\(x\inℤ\))

Vậy\(x=-9\)

\(b,2-x=17-\left(-5\right)\)

\(\Leftrightarrow2-x=22\)

\(\Leftrightarrow x=-20\)(Thỏa mãn\(x\inℤ\))

Vậy\(x=-20\)

\(c,\)\(x-12=\left(-9\right)-15\)

\(\Leftrightarrow x-12=-24\)

\(\Leftrightarrow x=-12\)(Thỏa mãn\(x\inℤ\))

Vậy\(x=-12\)

\(d,\)\(9-25=\left(7-x\right)-\left(25+7\right)\)

\(\Leftrightarrow-16=7-x-25-7\)

\(\Leftrightarrow x=-25+16\)

\(\Leftrightarrow x=-9\)(Thỏa mãn\(x\inℤ\))

Vậy\(x=-9\)

Hok tốt!

Good girl

cậu muốn gì hả Kurama

25.35.4

=25.4.35

=100.35

=3500

5.15.2

=5.2.15

=10.15

=150

x-9=0

    x=0+9

    x=9

x+10=10

      x=10-10

      x=0

25. 35 . 4 = ( 25 . 4 )  .35 = 100 . 35 = 3500

5 . 15 . 2 = ( 5 . 2 ) . 15 = 10 . 15= 150

Bài 2 : 

x - 9 = 0 => x = 0 + 9  => x = 9. Vậy x = 9

x + 10 = 10 => x = 10 - 10 => x = 0. Vậy x = 0

12,6 × x < 25

x < 25 : 12,5

x < 2

Vậy x = 0; x = 1

8x = 7,8x + 25

\(\Rightarrow\)8x - 7,8x = 25

\(\Rightarrow\)0,2x = 25

\(\Rightarrow\)x = 25 : 0,2

\(\Rightarrow\)x = 125

=>8x-7,8x=25

=>0,2x=25

=>x=125

       8x = 7,8x + 25

<=> 8x - 7,8x = 25

<=> 0,2x        = 25

<=> x             = 25 : 0,2

<=> x             = 125

1. bội của 3 \(\in\) { 3, 6, 9, 12, 15, ...}

nhưng B(3) \(\le\) 12

\(\Rightarrow B\left(3\right)\in\left\{3;6;9;12\right\}\)

2. \(B\left(4\right)\in\left\{4;8;12;16;20;24;28;...\right\}\)

nhưng  \(5< B\left(4\right)< 25\)

\(\Rightarrow B\left(4\right)\in\left\{8;12;16;20\right\}\)

3. \(Ư\left(8\right)\in\left\{1;2;4;8\right\}\)

4.  \(Ư\left(12\right)\in\left\{1;2;3;4;6;12\right\}\)

5.  \(Ư\left(5\right)\in\left\{1;5\right\}\)

6.  Ta có : \(Ư\left(9\right)\in\left\{1;3;9\right\}\)

mà \(x\inƯ\left(9\right)\)

Vậy: \(x\in\left\{1;3;9\right\}\)