a. (5.x + 3) : 4 – 16 = 6

(5.x + 3) : 4  = 22 

(5.x + 3)  = 88 

5.x  = 85

x = 13

b. 7(23 – 3.x) : 2 – 35 = 35

 7(23 – 3.x) : 2 = 70 

7(23 – 3.x) = 35 

 7 . 3.x = 12

7.x = 4 

x = 4/7 

a.) (5.x + 3) : 4 – 16 = 6

=> (5.x + 3) : 4  = 22

=> 5.x + 3  = 88

=>   5x  = 85 

=>   x  =  17

b) 7(23 – 3.x) : 2 – 35 = 35

=>  7(23 – 3.x) : 2  = 70

=>7(23 – 3.x)  = 140

=>   23 – 3.x  =  20

=>    3x    =  3 

=>   x  =  1 

a: =>3(x+4)=115

=>x+4=115/3

hay x=103/3

b: =>\(8^3\cdot\left(12x-64\right)=4\cdot8^4\)

\(\Leftrightarrow12x-64=32\)

=>12x=96

hay x=8

c: \(\Leftrightarrow\left(4x+28\right)\cdot23+55=175\)

=>(4x+28)x23=120

=>4x+28=120/23

=>4x=-524/23

hay x=-131/23

a: \(280-\left(x-140\right):35=270\)

=>(x-140):35=280-270=10

=>x-140=350

=>x=350+140

=>x=490

b: \(\left(190-2x\right):35-32=16\)

=>\(\left(190-2x\right):35=32+16=48\)

=>\(190-2x=35\cdot48=1680\)

=>2x=190-1680=-1490

=>x=-745

c: \(720:\left\lbrack41-\left(2x-5\right)\right\rbrack=2^3\cdot5\)

=>\(720:\left\lbrack41-\left(2x-5\right)\right\rbrack=8\cdot5=40\)

=>41-(2x-5)=720:40=18

=>2x-5=41-18=23

=>2x=28

=>x=14

d: \(\left(x:23+45\right)\cdot37-22=2^4\cdot105\)

=>\(\left(\frac{x}{23}+45\right)\cdot37=16\cdot105+22=1702\)

=>\(\frac{x}{23}+45=46\)

=>\(\frac{x}{23}=1\)

=>x=23

e: \(\left(3x-4\right)\left(x-1\right)^3=0\)

=>\(\left[\begin{array}{l}3x-4=0\\ x-1=0\end{array}\right.\Rightarrow\left[\begin{array}{l}x=\frac43\\ x=1\end{array}\right.\)

f: \(2^{2x-1}:4=8^3\)

=>\(2^{2x-1-2}=2^9\)

=>2x-3=9

=>2x=12

=>x=6

g: \(x^{17}=x\)

=>\(x^{17}-x=0\)

=>\(x\left(x^{16}-1\right)=0\)

=>\(\left[\begin{array}{l}x=0\\ x^{16}-1=0\end{array}\right.\Rightarrow\left[\begin{array}{l}x=0\\ x^{16}=1\end{array}\right.\Rightarrow\left[\begin{array}{l}x=0\\ x=1\\ x=-1\end{array}\right.\)

h: \(\left(x-5\right)^4=\left(x-5\right)^6\)

=>\(\left(x-5\right)^6-\left(x-5\right)^4=0\)

=>\(\left(x-5\right)^4\cdot\left\lbrack\left(x-5\right)^2-1\right\rbrack=0\)

=>\(\left(x-5\right)^4\cdot\left(x-4\right)\left(x-6\right)=0\)

=>x∈{4;5;6}

i: \(\left(x+2\right)^5=2^{10}\)

=>\(\left(x+2\right)^5=\left(2^2\right)^5=4^5\)

=>x+2=4

=>x=2

k: 1+2+3+...+x=78

=>\(\frac{x\left(x+1\right)}{2}=78\)

=>x(x+1)=156

=>\(x^2+x-156=0\)

=>(x+13)(x-12)=0

=>x=-13(loại) hoặc x=12(nhận)

l: \(\left(3x-2^4\right)\cdot7^3=2\cdot7^4\)

=>\(3x-16=2\cdot\frac{7^4}{7^3}=2\cdot7=14\)

=>3x=16+14=30

=>\(x=\frac{30}{3}=10\)

n: \(5^{x}:5^2=125\)

=>\(5^{x-2}=5^3\)

=>x-2=3

=>x=5

m: \(\left(x+1\right)^2=\left(x+1\right)^0\)

=>\(\left(x+1\right)^2=1\)

=>\(\left[\begin{array}{l}x+1=1\\ x+1=-1\end{array}\right.\Rightarrow\left[\begin{array}{l}x=0\\ x=-2\end{array}\right.\)

o: Số số hạng của dãy số 2;4;..;52 là:

(52-2):2+1=50:2+1=25+1=26(số)

Tổng của dãy số 2;4;...;52 là:

\(\left(52+2\right)\cdot\frac{26}{2}=54\cdot13=702\)

(2+x)+(4+x)+...+(52+x)=780

=>26x+702=780

=>26x=78

=>x=3

p: \(70=2\cdot5\cdot7;80=2^4\cdot5\)

=>ƯCLN(70;80)=\(2\cdot5=10\)

70⋮x; 80⋮x

=>x∈ƯC(70;80)

=>x∈Ư(10)

mà x>8

nên x=10

q: \(12=2^2\cdot3;25=5^2;30=2\cdot3\cdot5\)

=>BCNN(12;25;30)=\(2^2\cdot3\cdot5^2=300\)

x⋮12; x⋮25; x⋮30

=>x∈BC(12;25;30)

=>x∈B(300)

mà 0<x<500

nên x=300

a, 128 – 3(x+4) = 23

b,  12 x - 4 3 . 8 3 = 4 . 8 4

c, [(4x+28).3+55]:5 = 35

d, 720:[41 – (2x – 5)] =  2 3 . 5

a) x = 29

b) x = 1 và x = -5

c) x = 9 và x = -1

b. 1500(x-7)=0

x-7=0

x=7

c. (2x-4)(48-12x)=0

2x-4=0 hoặc 48-12x=0

x=2 hoặc x=4

d. (x+12)(x-1)=0

x+12=0 hoặc x-1=0

x=-12 hoặc x=1

bài 2 :

a . 128-3(x+4)=23

3(x+4)=105

x+4=35

x=31

b. [(14X+26).3+55]:5=35

(14x+26).3+55=175

(14x+26).3=120

14x+26=40

14x=14

x=1

d. 720:[41-(2X-5)]=23.5

41-(2x-5)=720:(23.5)

41-(2x-5)=144/23

2x-5=799/23

2x=914/23

x=457/23

b, 1500.(x – 7) = 0

<=>1500x-10500=0

<=>1500x=10500

<=>x=7

Vậy x=7

c,(2.x – 4).(48 – 12.x) = 0

\(\Leftrightarrow\)\(\left\{{}\begin{matrix}2x-4=0\\48-12x=0\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}2x=4\\12x=48\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}x=2\\x=4\end{matrix}\right.\)

Vậy x=2 hoặc x=4

d, (x + 12).(x – 1) =0

\(\Leftrightarrow\left\{{}\begin{matrix}x+12=0\\x-1=0\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}x=-12\\x=1\end{matrix}\right.\)

Vậy x=-12 hoặc x=1

Bài 2:

a) 128- 3(x+ 4) = 23

\(\Leftrightarrow\)128-(3x+12)=23

\(\Leftrightarrow\)128-3x-12=23

\(\Leftrightarrow\)116-3x=23

\(\Leftrightarrow\)3x=116-23

\(\Leftrightarrow\)3x=93

\(\Leftrightarrow\)x=31

Vậy x=31

b) [(14x+ 26). 3+ 55]: 5= 35

\(\Leftrightarrow\)(14x+ 26). 3+ 55=175

\(\Leftrightarrow\)42x+78+55=175

\(\Leftrightarrow\)42x+133=175

\(\Leftrightarrow\)42x=175-133

\(\Leftrightarrow\)42x=42

\(\Leftrightarrow\)x=1

Vậy x=1

d, 720: [41- (2x- 5)]= 23. 5

\(\Leftrightarrow\)720: 41- (2x- 5)=115

\(\Leftrightarrow\)41-(2x- 5)=720:115

\(\Leftrightarrow\)41-(2x- 5)=\(\dfrac{144}{23}\)

\(\Leftrightarrow\)2x-5=\(\dfrac{799}{23}\)

\(\Leftrightarrow\)2x=\(\dfrac{914}{23}\)

\(\Leftrightarrow\)x=\(\dfrac{457}{23}\)

Vậy x=\(\dfrac{457}{23}\)

a. 128 - 3 x (X + 2) = 23

             3 x (X + 2) = 128 - 23

                   X + 2    = 105 : 3

                    X         = 35 - 2

                    X         = 33

b. (12 x X - 64) x 8 = 4,64

    12 x X - 64         = 4,64 : 8

    12 x X                 = 0,58 + 64

        X                    = 64,58 : 12

         X                   = \(\frac{3229}{600}\)

c. [(4 x X + 28) x 3 + 55] : 5 = 35

    [(4 x X + 28) x 3 + 55]      = 35 x 5

       (4 x X + 28) x 3             = 175 - 55

        4 x X + 28                     = 120 : 3

         4 x  X                           = 40 - 28

          X                                 = 12 : 4

          X                                 = 3

d. 720 : [41 - (2 x X - 5)] = 8 x 5

              41 - (2 x X - 5)  = 720 : (8 x 5)

                    2 x X - 5      = 41 - 18

                   2 x X            = 23 + 5 

                       X              = 28 : 2

                       X              = 14

x nhỏ : dấu nhân

X lớn : X 

128 - 3 ( x + 4 ) = 23

         3 ( x + 4 ) = 128 - 23

         3 ( x + 4 ) = 105

              x + 4   = 105 : 5

              x + 4   = 35

              x         = 35 - 4

              x         = 31

128 - 3 ( x + 4 ) = 23

         3 ( x + 4 ) = 128 - 23

         3 ( x + 4 ) = 105

              x + 4   = 105 : 5

              x + 4   = 35

              x         = 35 - 4

              x         = 31

k mik nha

a,

128-3x-12=23

3x=128-12-23

3x=93

x=93:3

= 31

b,

(12x+84+55):5=35

12x+84+55=35.5

12x+84+55=175

12x=175-55-84

12x=36

x=36:12

x=3