\(\left(84,6-2\cdot x\right):3,02=5,1\)

\(\Rightarrow84,6-2\cdot x=15,402\)

\(\Rightarrow2\cdot x=69,198\)
\(\Rightarrow x=69,198:2\)

\(\Rightarrow x=34,599\)

_____________

\(\left(15\cdot24-x\right):0,25=100:0,25\)

\(\Rightarrow\left(360-x\right):0,25=400\)

\(\Rightarrow360-x=100\)

\(\Rightarrow x-360-100\)

\(\Rightarrow x=260\)

______________

\(128\cdot x-12\cdot x-16\cdot x=5200\)

\(\Rightarrow x\cdot\left(128-12-16\right)=5200\)

\(\Rightarrow x\cdot100=5200\)

\(\Rightarrow x=5200:100\)

\(\Rightarrow x=52\)

__________________

\(5\cdot x+3,75\cdot x+1,25\cdot x=20\)

\(\Rightarrow x\cdot\left(5+3,75+1,25\right)=20\)

\(\Rightarrow10\cdot x=20\)

\(\Rightarrow x=20:10\)

\(\Rightarrow x=2\)

\(x\cdot3,7+x\cdot6,3=360:120\)

\(\Rightarrow x\cdot\left(3,7+6,3\right)=3\)

\(\Rightarrow x\cdot10=3\)

\(\Rightarrow x=\dfrac{3}{10}\)

__________________

\(x\cdot23-6\cdot23+x\cdot69=320\)

\(\Rightarrow x\cdot\left(23+69\right)=320+6\cdot23\)

\(\Rightarrow x\cdot92=458\)

\(\Rightarrow x=458:92\)

\(\Rightarrow x=\dfrac{229}{46}\)

___________________

\(\left(x+1\right)\left(x+2\right)=72\)

\(\Rightarrow x^2+2x+x+2=72\)

\(\Rightarrow x^2+3x+2=72\)

\(\Rightarrow x^2+3x+2-72=0\)

\(\Rightarrow x^2+3x-70=0\)

\(\Rightarrow x^2+10x-7x-70=0\)

\(\Rightarrow\left(x-7\right)\left(x+10\right)=0\)

\(\Rightarrow\left[{}\begin{matrix}x=7\\x=-10\end{matrix}\right.\)

___________________

\(\left(x+2\right)\cdot16\cdot x=160x\)

\(\Rightarrow16x^2+32x=160x\)

\(\Rightarrow16x^2+32x-160x=0\)

\(\Rightarrow16x^2-128x=0\)

\(\Rightarrow16x\left(x-8\right)=0\)

\(\Rightarrow\left[{}\begin{matrix}x=0\\x=8\end{matrix}\right.\)

Đổi:

f.x.23-6.23+x.69=230

=>23.(x-6+3x)=230

=>4x-6=10

=>4x=10+6

=>4x=16

=>x=4

h.(x+2).16.x=160.x

=>(16x+32).x = 160x

=>16x^2 + 32x = 160x

=>16x^2 = 128x

=>16x^2 - 128x=0

=>x(16x-128)=0

=>x=0 hoặc 16x-128=0

+)x=0=>x=0

+)16x-128=0

=>16x=128

=>x=8

( 15,25 - x ) : 25 = 400

=> 15,25 - x = 10000

=> x = - 9984,75

\(\left(15,24-x\right):25=400\)

\(15,24-x=10000\)

\(x=15,24-10000\)

\(x=-998476\)

Vậy x = -998476

15*24+76*15+(-1500)=15*(24+76)+(-1500)=15*100+(-1500)=1500+(-1500)=0

15.24 + 76.15 + ( - 1500 )

​= 360 + 1140 + ( -1500 )

​= 1500 + ( -1500 )

= 0

Tick nha

\(5.7.77-7.60+49.25-15.42\)

\(=5.7.77-7.5.12+49.5.5-5.3.42\)

\(=5.539-84.5+245.5-5.126\)

\(=5.\left(539-84+245-126\right)\)

\(=5.547\)

\(=2870\)

3140

13 + 21.5 - (198 : 11 - 8)

= 13 + 105 - 10

= 108

272 : 16 - 5 +4 (30 - 5 - 255 : 17)

= 17 - 5 + 4. ( 30 - 5 - 15 )

= 16 . 10

= 160

15.24 - 14.5 (145 : 5 - 27)

= 360 - 70 ( 29 - 27 )

= 290 . 2

= 580

18.3 - 18.2 + 3 (51 : 17)

= 54 - 36 + 3 . 3

= 54 - 36 + 9

= 27

(64 + 115 + 36) - 25.8

= 215 - 200 

= 15

15.8 - (17 - 30 + 83) - 144 : 6

= 120 - 70 - 24

= 26

250 : 50 - (46 - 75 + 54) : 5

= 5 - 25 : 5 

= 5 - 5

= 0

13 (17 - 95 + 83) : 5 - 18 : 9

= 13. 5 : 5 - 2

= 65 : 5 - 2

= 13 - 2

= 11

140 - 180(47 - 90 + 43) + 7

= 140 - 180 . 0 + 7

= 140 + 7

= 147

24 (15 + 30 + 85 - 120):10

= 24. 10 : 10 

= 240 : 10

= 24

27 + 73 - 30 : (25 -10)

= 27 + 73 - 30 : 15

= 27 + 73 - 2

= 98

18 - 4 (27 - 90 + 73) : 10

= 18 - 4. 10 : 10

= 18 - 40 : 10

= 18 - 4

= 14

Bài 2: Tính

140 - [ 25 : (4 mũ 2 - 11) + 4 ]

= 140 - [25 : (16 - 11) + 4 ]

= 140 - [ 25 : 5 + 4 ]

= 140 - [ 5 + 4]

= 140 - 9 

= 131

giúp mik nhé cám ơn

16

=28

      A=100/1 x 2 + 100/2 x 3 + 100/3 x 4 +...+100/99 x 100

A/100=1/1 x 2 + 1/2 x 3 + 1/3 x 4 +...+1/99 x 100

A/100=2-1/1x2 + 3-2/2x3 + ... + 100-99/99x100

A/100=1-1/2 + 1/2-1/3+...+1/99-1/100

A/100=1-1/100

A/100=99/100

A=99/100x100=99

Vậy A=99.

Ta có:

\(\frac{100}{1.2}+\frac{100}{2.3}+\frac{100}{3.4}+...+\frac{100}{99.100}\)

\(\Rightarrow100.\left(\frac{1}{1.2}+\frac{1}{2.3}+\frac{1}{3.4}+...+\frac{1}{99.100}\right)\)

\(\Rightarrow100.\left(\frac{1}{1}-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+...+\frac{1}{99}-\frac{1}{100}\right)\)

\(\Rightarrow100.\left(\frac{1}{1}-\frac{1}{100}\right)\Leftrightarrow100.\frac{99}{100}=99\)

\(\text{Ta có :}\)

\(\frac{100}{1.2}+\frac{100}{2.3}+\frac{100}{3.4}+...+\frac{100}{99.100}\)

\(=100.\left(\frac{1}{1}-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+...+\frac{1}{99}-\frac{1}{100}\right)\)

\(100.\left(\frac{1}{1}-\frac{1}{100}\right)=100.\frac{99}{100}=99\)