thế thì hiếm người trả lời đầy đủ cho bn lắm 

3120

Bài 1:

1: \(12\cdot18+14\cdot3-255:17\)

=216+42-15

=216+27

=243

2: \(68+42\cdot5-625:25\)

=68+210-25

=43+210

=253

3: \(13+21\cdot5-\left(198:11-18\right)\)

=13+105-(18-18)

=13+105

=118

4: \(272:16-5+4\cdot\left(30-5-255:17\right)\)

=17-5+4(25-15)

\(=12+4\cdot10=12+40=52\)

5: \(25\cdot8-12\cdot5+272:17-8\)

=200-60+16-8

=140+8

=148

6: \(125:25+14-142:71\)

=5+14-2

=19-2

=17

7: \(13\cdot17-256:16+14:7-1\)

=221-16+2-1

=205+1

=206

8: \(15\cdot24-14\cdot5\cdot\left(145:5-27\right)\)

\(=360-70\cdot\left(29-27\right)\)

=360-140

=220

9: \(289:17-324:18+18:3\)

=17-18+6

=-1+6

=5

10: \(18\cdot3-182+3\cdot\left(51:17\right)\)

=54-182+9

=63-182

=-119

11: (64+115+36)-\(25\cdot8\)

=100+115-200

=115-100

=15

12: \(15\cdot8-\left(17-30+83\right)-144:6\)

=120-(100-30)-24

=120-70-24

=50-24

=26

13: \(19+19\cdot99-25\cdot8\)

\(=19\left(1+99\right)-200\)

=1900-200

=1700

14: \(250:50-\left(46-75+84\right):5\)

=5-(130-75):5

=5-55:5

=5-11

=-6

15: \(13\left(17-95+83\right):5-18:9\)

\(=13\cdot\frac{\left(100-95\right)}{5}-2\)

=13-2

=11

16: \(140-180\left(47-90+43\right)+7\)

\(=140-180\cdot\left(90-90\right)+7\)

=140+7

=147

17: \(24\left(15+30+85-120\right):10\)

\(=24\cdot\left(100+30-120\right):10\)

\(=24\cdot\frac{10}{10}=24\)

18: \(27+73-30:\left(25-10\right)\)

=100-30:15

=100-2

=98

19: \(18-4\left(27-90+73\right):10\)

\(=18-\frac{4\left(100-90\right)}{10}\)

=18-4

=14

20: \(15-25\cdot8:\left(100\cdot2\right)\)

=15-200:200

=15-1

=14

Bài 2:

1: \(13\cdot58\cdot4+32\cdot26\cdot2+52\cdot10\)

\(=52\cdot58+52\cdot32+52\cdot10\)

\(=52\cdot\left(58+32+10\right)=52\cdot100=5200\)

2: \(15\cdot37\cdot4+120\cdot21+21\cdot5\cdot12\)

\(=60\cdot37+60\cdot42+60\cdot21\)

\(=60\cdot\left(37+42+21\right)=60\cdot\left(58+42\right)=60\cdot100=6000\)

$x^2-2x-(x-7)(x+2)\\=x^2-2x-x^2+5x+14\\=3x+14$

-1-1/2-1/4-1/8......-1/1024

=-(1+1/2+1/4+1/8...+1/1024)

mà ta có 1024=2^10

nên -(1+1/2+1/4+1/8...+1/1024)

=-(2^9+2^8+2^7....+1)/2^10

=-(1023/1024)

=-1,99.........

mình sẽ làm lại bai này cho đúng nha

\(-1-\frac{1}{2}-\frac{1}{4}....-\frac{1}{1024}=-1-\left(\frac{1}{2}+\frac{1}{4}+...\frac{1}{1024}\right)\)

\(=-1-\left(\frac{1}{2^1}+\frac{1}{2^2}...+\frac{1}{2^{10}}\right)\)

\(=-1-\frac{1023}{1024}=\frac{-1024}{1024}-\frac{1023}{1024}=\frac{-2047}{1024}\)

vậy mới đúng nha

Dãy số cách đều 1 đơn vị có Tổng là:

\(S=\frac{\left(x+1\right)}{2}\cdot\left(\frac{x-1}{1}+1\right)=\frac{x\left(x+1\right)}{2}=45\)

=> x(x+1) = 90 = 9*10

=> x = 9
 

ê mọi người ấy chỉ muốn **** à

Được vậy bạn giải giùm mình nha đề bài nè :Tính hợp lý(nếu có thể) a)7^5:7^3+3^2.2^3-2009^() b)5^3.52+5^3.7^2-5^3 c)[130-3.(5.2^4-5^2.2)]2^3 d)10+12+14+....+148+150  Tìm x€N a)8.(x-5)+17=17 b)125-5.(3x-1)=5^5:5^3 c)4^x+1 +4^()=65
 

MK KO CÓ SGK

a) 108 . 28 = (10.2)8 = 208

b) 108 : 28 = (10:2)8 = 58

c) 254 . 28 = 58 . 28 = 108

d) 158 . 94 = 158 . 38 = 458

e) 272 : 253 = (33)2 : (52)3 = 33.2 : 52.3 = 36 : 56 =