a,10x+65=125

   10x      =125-65

       x      =60:10

       x      =6

Vậy:...

b,45-(5-2x)^3=2.3^2

   45-(5-2x)^3=18

    (5-2x)^3    =45-18

    (5-2x)^3    =27=3^3

=> 5-2x  = 3

     2x = 5-3

     x= 2:2

     x=1

Vậy:....

-Hok tốt ~ K mk nhak.

a, 10x + 65 = 125

10x = 125 - 65

10x = 60

x = 60 : 10

x = 6

b,45-(5-2x)^3=2.3^2

45 - ( 5 - 2x )^3 =18

(5 - 2x)^3 = 45 - 18

(5 - 2x )^3= 3^3

5 - 2x = 3

2x = 2

x = 1

c,2(x-3)-12=(-10)

2x - 6 -12 =-10

2x = -10 + 6 + 12

2x = 8

x = 4

d,x-12=(-13)+1+|-13|

x - 12 = -13 + 1 + 13

x - 12 = 1

x = 13

hok tốt!!!

Bài 15:

a: 2x+x=45

=>3x=45

=>\(x=\frac{45}{3}=15\)

b: 2x+7x=918

=>\(x\cdot\left(7+2\right)=918\)

=>9x=918

=>\(x=\frac{918}{9}=102\)

c: 2x+3x=60+5

=>5x=65

=>\(x=\frac{65}{5}=13\)

d: \(11x+22x=33\cdot2\)

=>33x=66

=>\(x=\frac{66}{33}=2\)

Bài 14:

a: (12-x)(2-x)=0

=>\(\left[\begin{array}{l}12-x=0\\ 2-x=0\end{array}\right.\Rightarrow\left[\begin{array}{l}x=12\\ x=2\end{array}\right.\)

b: (x-33)(11-x)=0

=>\(\left[\begin{array}{l}x-33=0\\ 11-x=0\end{array}\right.\Rightarrow\left[\begin{array}{l}x=33\\ x=11\end{array}\right.\)

c: (21-x)(12-x)=0

=>\(\left[\begin{array}{l}21-x=0\\ 12-x=0\end{array}\right.\Rightarrow\left[\begin{array}{l}x=21\\ x=12\end{array}\right.\)

d: (50-x)(x-150)=0

=>\(\left[\begin{array}{l}50-x=0\\ x-150=0\end{array}\right.\Rightarrow\left[\begin{array}{l}x=50\\ x=150\end{array}\right.\)

Bài 13:

a: (x-2)(x-3)=0

=>\(\left[\begin{array}{l}x-2=0\\ x-3=0\end{array}\right.\Rightarrow\left[\begin{array}{l}x=2\\ x=3\end{array}\right.\)

b: (x-3)(x-4)=0

=>\(\left[\begin{array}{l}x-3=0\\ x-4=0\end{array}\right.\Rightarrow\left[\begin{array}{l}x=3\\ x=4\end{array}\right.\)

c: (x-7)(6-x)=0

=>\(\left[\begin{array}{l}x-7=0\\ 6-x=0\end{array}\right.\Rightarrow\left[\begin{array}{l}x=7\\ x=6\end{array}\right.\)

d: (x-3)(x-13)=0

=>\(\left[\begin{array}{l}x-3=0\\ x-13=0\end{array}\right.\Rightarrow\left[\begin{array}{l}x=3\\ x=13\end{array}\right.\)

33/5

giải chi tiết giúp mình nhé

\(a,\)\(x+\frac{4}{5.9}+\frac{4}{9.13}+\frac{4}{13.17}+...+\frac{4}{41.45}=-\frac{37}{45}\)

  \(x+\left(\frac{9-5}{5.9}+\frac{13-9}{9.13}+\frac{17-13}{13.17}+...+\frac{45-41}{41.45}\right)=-\frac{37}{45}\)

  \(x+\left(\frac{1}{5}-\frac{1}{9}+\frac{1}{9}-\frac{1}{13}+\frac{1}{13}-\frac{1}{17}+....+\frac{1}{41}-\frac{1}{45}\right)-\frac{37}{45}\)

 \(x+\left(\frac{1}{5}-\frac{1}{45}\right)=-\frac{37}{45}\)

 \(x+\frac{8}{45}=-\frac{37}{45}\)

\(x=-\frac{37}{45}-\frac{8}{45}\)

\(x=-1\)

thế phần b, c đâu bạn

a,x+9=20-(12-75)-(-8)

  x+9=20-(-63) + 8

  x+9 = 20 + 63 + 8

  x+9 = 91

   x    = 91 - 9

   x    = 82.

Vậy x = 82.

b,2.|x-3|=16-(-3)-(-13)-2

 2.|x-3|=16 + 3 + 13 - 2

  2.|x-3|= 30

     |x-3| = 30:2

     |x-3| = 15

\(\Rightarrow\orbr{\begin{cases}x-3=15\\x-3=-15\end{cases}}\)\(\Rightarrow\orbr{\begin{cases}x=18\\x=-12\end{cases}}\)

Vậy x \(\in\){ 18 ; -12 }

# HOK TỐT #

a, x+9=20-(12-75)-(-8)

x+9=91

x    =91-9

x    =82

b,2.|x-3|=16-(-3)-(-13)-2

2.|x-3| =30

|x-3|=30:2

|x-3|=15

--> x-3=15             hoặc              x-3= -15

    x=15+3                                    x= -15+3

     x=18                                       x= -12

Vậy x thuộc {18;-12}

Chọn đáp án D