a) 3x – 2 = 19

3x = 19 + 2

3x = 21

x = 21:3

x = 7

b) [43 - (56 - x)].12 = 384

43 – (56 – x) = 384:12

43 – (56 – x) = 32

56 – x = 43 – 32

56 – x = 11

x = 56 – 11

x = 45

c) 3^x.2 + 15 = 33

3^x.2 = 33 - 15

3^x.2 = 18

3^x = 18 : 2

3^x = 9

3^x = 33

x = 2.

a) 3x – 2 = 19

3x = 19 + 2

3x = 21

x = 21:3

x = 7

b) [43 - (56 - x)].12 = 384

43 – (56 – x) = 384:12

43 – (56 – x) = 32

56 – x = 43 – 32

56 – x = 11

x = 56 – 11

x = 45

c) 3^x.2 + 15 = 33

3^x.2 = 33 - 15

3^x.2 = 18

3^x = 18 : 2

3^x = 9

3^x = 33

x = 2.

a: x+4/9=19/24

=>x=19/24-4/9=25/72

b: x-5/8=17/12

=>x=5/8+17/12=49/24

\(x+\)\(\dfrac{4}{9}=\dfrac{19}{24}\)

\(x=\)\(\dfrac{19}{24}-\dfrac{4}{9}\)

\(x=\)\(\dfrac{171-96}{216}=\dfrac{75}{216}\)

\(x-\)\(\dfrac{5}{8}=\dfrac{17}{12}\)

\(x=\)\(\dfrac{17}{12}+\dfrac{5}{8}\)

\(x=\)\(\dfrac{136+60}{96}=\dfrac{196}{96}\)

a) không có số nào

B) chịu

sao lạ vại men, ko còn ý kiến nào hay hơn à

U LÀ TRỜI

x=-538

\(a,12-5x=35:5\\12-5x=7\\5x=12-7\\5x=5\\x=5:5\\x=1\\b,4-2(1-x)=2^3:4\\\\4-2(1-x)=8:4\\4-2(1-x)=2\\2(1-x)=4-2\\2(1-x)=2\\ 1-x=2:2\\1-x=1\\ x=1-1\\ x=0\)

x+12=23

x      =23-12

x     =11

34-x=32

     x=34-32

     x=2

x-56=45

x    =45+56

x    =101

x=35

x=2

x=101

bài 2 tìm x

a,106- ( x+ 7) =9

x+7 = 106 - 9

x+7 = 107

x= 107 - 7

x=100

b, 2 x ( x+ 4) + 5 =65

2 x (x+4) = 65 - 5

2 x (x+4) = 60

x+4 = 60:2

x+4= 30

x= 30 - 4

x=26

c, (16x x -32) x 45=0

16 x X - 32 = 0: 45

16 x X - 32 =0

16 x X = 0 + 32

16 x X = 32

X= 32:16

X=2

d, x+4 x x = 100 : 5

X + 4 x X = 20

(1+4) x X = 20

5 x X  = 20

X= 20:5

X=4

Bài 1:

a, 24 x 66 - 24 + 36 x 24

= 24 x (66-1+36)

= 24 x 101

= 24 x 100 + 24

= 2400+24

=2424

b, 29 x 173 - 29 x 72 - 29

= 29 x (173 - 72 -1)

= 29 x 100

= 2900

c, 1+5+10+15+...+55+60

= (5+60) x 6 + 1 (có 6 cặp)

= 65 x 6 + 1

= 390 +1 =391

d, D= 1 x 2 + 2 x 3 + 3 x 4 +...+18 x 19 + 19 x 20

3D= 1 x 2 x 3+ 2 x 3 x (4-1) + 3 x 4 x (5-2) +...+ 18 x 19 x (20 - 17) + 19 x 20 x (21-18)

3D= 1 x 2 x 3 - 1 x 2 x 3 + 2 x 3 x 4 - 2 x 3 x 4 +.... + 19 x 20 x 21 - 18 x 19 x 20

3D= 19 x 20 x 21 =7980

=> D= 7980:3=2660