a,  2 3 x + 5 2 x = 2 5 2 + 2 3 - 33

8x+25x = 33

33x = 33

x = 1

b,  260 : x + 4 = 5 2 3 + 5 - 3 3 2 + 2 2

260:(x+4) = 5.13–3.13

x+4 = 260:26

x+4 = 10

x = 6

c,  720 : [ 41 - 2 x - 5 ] = 2 3 . 5

41–(2x–5) = 720:40

2x–5 = 41–18

2x = 28

x = 14

d,  3 2 - 2 x - 12 + 35 = 5 2 + 279 : 3 2

7(x–12)+35 = 56

7(x–12) = 21

x–12 = 3

x = 15

Bài 2: Tính nhanh

a) 29 + 132 + 237 + 868 + 3

 = 29+(132+858)+(237+3)

=29+990+240

=1259

29+132+237+868+3

29+(132+868)+(237+3)

29+1000+240

29+(1000+240)

29+1240

1269

bài 2 :

a) 29 + 132 + 237 + 868 + 3

= 29 +(132 + 868)+(237 + 3)

= 29 + 1000 + 240

=1269

b) 35 . 34 + 35 . 86 + 65 . 75 + 65 . 5
= 35 .(34 + 86)+ 65 .(75 + 5)

= 35 . 120 + 65 . 80

= 4200 + 5200

= 9400

c) 3 . 25 . 8 + 4 . 37 . 6 + 2 . 38 .12

khum bít làm hehe

d) 12 . 53 + 53 . 172 - 53 . 84

= 53 . (12 + 172 - 84)

= 53 . 100

= 5300

Bài 3:

a) 4 . 52 - 18 : 32 hình như câu này sai đề

b) 32 . 22 - 32 . 19

= 32 . (22 - 19)

= 32 . 3

= 96

\(a,3x-30=3^5:3^2\\ \Rightarrow3x-30=3^3\\ \Rightarrow3x-30=27\\ \Rightarrow3x=57\\ \Rightarrow x=19\\ b,120-4\left(9+x\right)=16\\ \Rightarrow4\left(9+x\right)=104\\ \Rightarrow9+x=26\\ \Rightarrow x=17\)

Đáp Án

a)52:4x3+2x52

=13x3+2x52

=39+104

=143

b)5x42-18:32

=100-0.5625

=99.4375

của bạn nha

x - ( 17 - x ) = x + 3

<=> 2x - 17  = x + 3 

<=> x = 20

Vậy x = 20

- ( x + 12 ) + 35 = - 47

<=> - x - 12 = - 47 -35

<=> x = 47 + 35 - 12

<=> x = 60

Vậy x = 60

15 - ( x + 32 ) = - 11

<=> 15 - x - 32 = - 11

<=> - x - 17 = - 11

<=> - x = - 11 + 17 = 6

<=> x = - 6

Vậy x = - 6

K chắc lắm

a)\(x-\left(17-x\right)=x+3\)

\(\Leftrightarrow x-17+x=x+3\)

\(\Leftrightarrow x+x-x=17+3\)

\(\Leftrightarrow x=20\)

b)\(-\left(x+12\right)+35=-47\)

\(\Leftrightarrow-x-12+35=-47\)

\(\Leftrightarrow-x=-47+12-35\)

\(\Leftrightarrow-x=-70\)

\(\Leftrightarrow x=70\)

c)\(15-\left(x+32\right)=-11\)

\(\Leftrightarrow15-x-32=-11\)

\(\Leftrightarrow-x=-11-15+32\)

\(\Leftrightarrow-x=6\)

\(\Leftrightarrow x=-6\)

x - ( 17 - x ) = x + 3

   x - 17 + x = x + 3

   x + x - x   = 3 + 17

              x   = 20

Vậy x = 20

- ( x + 12 ) + 35 = - 47

     - x - 12 + 35 = - 47

                    - x = - 47 + 12 - 35

                    - x = - 70

                      x = 70

Vậy x = 70

15 - ( x + 32 ) = - 11

         x + 32   = 15 - ( - 11 )

         x + 32   = 26

                x    = 26 - 32

                x    = - 6

Vậy x = - 6

Bài 1

S₂ = 21 + 23 + 25 + ... + 1001

Số số hạng của S₂:

(1001 - 21) : 2 + 1 = 491

⇒ S₂  = (1001 + 21) . 491 : 2 = 250901

--------

S₄  = 15 + 25 + 35 + ... + 115

Số số hạng của S₄:

(115 - 15) : 10 + 1 = 11

⇒ S₄ = (115 + 15) . 11 : 2 = 715

Bài 2

a) 2x - 138 = 2³.3²

2x - 138 = 8.9

2x - 138 = 72

2x = 72 + 138

2x = 210

x = 210 : 2

x = 105

b) 5.(x + 35) = 515

x + 35 = 515 : 5

x + 35 = 103

x = 103 - 35

x = 78

c) 814 - (x - 305) = 712

x - 305 = 814 - 712

x - 305 = 102

x = 102 + 305

x = 407

d) 20 - [7.(x - 3) + 4] = 2

7(x - 3) + 4 = 20 - 2

7(x - 3) + 4 = 18

7(x - 3) = 18 - 4

7(x - 3) = 14

x - 3 = 14 : 7

x - 3 = 2

x = 2 + 3

x = 5

e) 9ˣ⁻¹ = 9

x - 1 = 1

x = 1 + 1

x = 2

2:

a: \(2x-138=2^3\cdot3^2\)

=>\(2x-138=8\cdot9=72\)

=>2x=138+72=210

=>x=105

b: \(5\cdot\left(x+35\right)=515\)

=>x+35=103

=>x=103-35=68

c: \(814-\left(x-305\right)=712\)

=>x-305=814-712=102

=>x=102+305=407

d: \(20-\left[7\left(x-3\right)+4\right]=2\)

=>7(x-3)+4=18

=>7(x-3)=14

=>x-3=2

=>x=5

e: \(9^{x-1}=9\)

=>x-1=1

=>x=2

f: \(5^{x-2}-3^2=2^4-\left(2^8\cdot2^2-2^{10}\cdot2^2\right)\)

=>\(5^{x-2}-9=16-1024+4096\)

=>\(5^{x-2}=3097\)

=>\(x-2=log_53097\)

=>\(x=2+log_53097\)

92 + 71 + 108 = (92 + 108) + 71 = 200 + 71 = 271

32 x 47 + 53 x 47 + 47 x 15 = 47(32 + 53 + 15)

                                         = 47.100

                                         = 4700

90 x 143 - 43 x 90 = 90.(143 - 43) = 90.100 = 9000

(1200 + 60) : 12 = 1800 : 12 = 150

2 x 18 x 24 + 3 x 50 x 16 + 12 x 32 x 4 = 18.(2.24) + 50.(3.16) + 32.(12.4) = 18.48 + 50.48 + 32.48 = 48(18 + 50 + 32) = 48.100 = 4800

92+71+108=71+92+108=71+200=271

92+71+108=71+(92+108)=71+200=271

90x143-43x90=90x(143-43)=90x100=9000

32x47+53x47+47x15=47x(32+53+15)=47x100=4700

(1200+60):12=1260:12=105

2x18x24+3x50x16+12x32x4=(2x24)x18+(3x16)x50+(12x4)x32

=48x18+48x50+48x32

=48x(18+50+32)

=48x100=4800

\(\text{35 + (–47) – |–12|}\)

\(=-12-12\)

\(=-24\)

\(\text{(–15) – 70 : (–14) + (–32) . (–2)}\)

\(=-15+5+64\)

\(=-10+64\)

\(=54\)

\(\text{ 15 – 12 . (-3)^2 – 135 : |–15|}\)

\(=15-12.9-135:15\)

\(=15-108-9\)

\(=-102\)

Tính hợp lý:

\(\text{ –24 . 78 + 24(–35) – 24(–13)}\)

\(=24.\left(-78+\left(-35\right)-\left(-13\right)\right)\)

\(=24.\left(-100\right)\)

\(=-2400\)

học tốt