D

D

D

(55⁶)² x (55⁹)⁵ = 55^6x2 x 55^9x5 = 55¹² x 55⁴⁵ = 55⁴⁷

1000¹⁰ x 1000⁵⁶ = 1000⁷⁶

550⁹⁵ x 550⁵ =550¹⁰⁰

D

B. 10

`@` `\text {Ans}`

`\downarrow`

`a)`

`x + 10 = 20`

`=> x = 20 -10`

`=> x = 10`

Vậy, `x = 10`

`b)`

`2 * x + 15 = 35`

`=> 2x = 35 - 15`

`=> 2x = 20`

`=> x = 20 \div 2`

`=> x = 10`

Vậy, `x = 10`

`c)`

`3 * ( x + 2 ) = 15`

`=> x + 2 = 15 \div 3`

`=> x + 2 = 5`

`=> x = 5 - 2`

`=> x = 3`

Vậy, `x = 3`

`d)`

`10 * x + 15 * 11 = 20 * 10`

`=> 10x + 165 = 200`

`=> 10x = 200 - 165`

`=> 10x = 35`

`=> x = 35 \div 10`

`=> x = 3,5`

Vậy,` x = 3,5`

`e)`

`4 * ( x + 2 ) = 3 * 4`

`=> x + 2 = 12 \div 4`

`=> x + 2 = 3`

`=> x = 3 - 2`

`=> x = 1`

Vậy,` x = 1`

`f)`

`33 x + 135 = 26 * 9`

`=> 33x + 135 = 234`

`=> 33x = 234 - 135`

`=> 33x = 99`

`=> x = 99 \div 33`

`=> x = 3`

Vậy, `x = 3`

`g)`

`2 * x + 15 + 16 + 17 = 100`

`=> 2x + 48 = 100`

`=> 2x = 100 - 48`

`=> 2x = 52`

`=> x = 52 \div 2`

`=> x =26`

`h)`

`2 * (x + 9 + 10 + 11) = 4 . 12 . 25`

`=> 2 * (x + 9 + 10 + 11) = 4*25*12`

`=> 2 * (x + 9 + 10 + 11) = 100*12`

`=> x + 9 + 10 + 11 = 100*12 \div 2`

`=> x + 30 = 600`

`=> x = 600 - 30`

`=> x = 570`

Vậy, `x = 570.`

a) \(x+10=20\Leftrightarrow x=10\)

b) \(2x+15=35\Leftrightarrow2x=20\Leftrightarrow x=10\)

c) \(3.\left(x+2\right)=15\Leftrightarrow x+2=5\Leftrightarrow x=3\)

d) \(10x+15.11=20.10\Leftrightarrow10x+165=200\Leftrightarrow10x=35\Leftrightarrow x=\dfrac{35}{10}=\dfrac{7}{2}\)

e) \(4.\left(x+2\right)=3.4\Leftrightarrow x+2=3\Leftrightarrow x=1\)

f) \(35x+135=26.9\Leftrightarrow35x=234-135\Leftrightarrow35x=99\Leftrightarrow x=\dfrac{99}{35}\)

g) \(2x+15+16+17=100\Leftrightarrow2x+48=100\Leftrightarrow2x=52\Leftrightarrow x=26\)

h) \(2.\left(x+9+10+11\right)=4.12.25\)

\(\Leftrightarrow x+30=2.12.25\)

\(\Leftrightarrow x=600-30\)

\(\Leftrightarrow x=570\)

ai nhanh nhất mình k cho

Bài 1:

\(A=\frac{1}{\left(1+2\right)}+\frac{1}{\left(1+2+3\right)}+\frac{1}{\left(1+2+3+4\right)}\)\(+\frac{1}{\left(1+2+3+4+5\right)}+...+\)\(\frac{1}{\left(1+2+3+...+10\right)}\)

\(A=\frac{1}{3}+\frac{1}{6}+....+\frac{1}{55}\)

\(A=2\left(\frac{1}{6}+\frac{1}{12}+....+\frac{1}{110}\right)\)

\(A=2\left(\frac{1}{2.3}+\frac{1}{3.4}+...+\frac{1}{10.11}\right)\)

\(A=2\left(\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+....+\frac{1}{10}-\frac{1}{11}\right)\)

\(A=2.\left(\frac{1}{2}-\frac{1}{11}\right)\)

\(A=\frac{9}{11}\)

Bài 2 :

2)  Tử số = 11 x 13 x 15 + 3 x 3 x 3 x 11 x 13 x 15 + 5 x 5 x 5 x 11 x 13 x 15 + 9 x 9 x 9 x 11 x 13 x 15

= (1 + 3 x 3 x 3 + 5 x 5 x 5 + 9 x 9 x9) x 11 x 13 x 15 = (1+27+125+ 729) x 11 x 13 x 15

Mẫu số =  11 x 13 x 17 + 3 x 3 x 3 x 13 x 15 x 19  + 5 x 5 x 5 x 13 x 15 x 17 + 9 x 9 x 9 x 13 x 15 x 17 lớn hơn 11 x 13 x 15 + 3 x 3 x 3 x 13 x 15 x 17 + 5 x 5 x 5 x 13 x 15 x 17 + 9 x 9 x 9 x 13 x 15 x 17  

=  (1 + 3 x 3 x 3 + 5 x 5 x 5 + 9 x 9 x9) 13 x 15 x  17 = (1+27+125+729) x 13 x 15 x 17 

\(\Rightarrow A< \frac{\left(1+27+125+729\right)\times11\times13\times15}{\left(1+27+125+729\right)\times13\times15\times17}\)

\(=\frac{11}{17}\)

\(=\frac{1111}{1717}=B\)

Vậy \(A=B\)

mình đâu biết

Bài 2:

a) 11. x = -55

x = -55 : 11

x = -5

Vậy x = -5

b) -3 . x = -12

x = -12 : (-3)

x = 4

Vậy x = 4

c) 3x - 12 = -48

3x = -48 + 12

3x = -36

x = -36 : 3

x = -12

Vậy x = -12

d) 10 + 23 . (2x - 10) = -36

23 . (2x - 10) = -36 - 10

23 . (2x - 10) = -46

2x - 10 = -46 : 23

2x - 10 = -2

2x = -2 + 10

2x = 8

x = 8: 2

x = 4

Vậy x = 4

f) | 2x - 1| + 3 = 8

|2x - 1| = 8 - 3

|2x - 1| = 5

\(\Rightarrow\left[\begin{matrix}2x-1=5\\2x-1=-5\end{matrix}\right.\Rightarrow\left[\begin{matrix}2x=6\\2x=-4\end{matrix}\right.\Rightarrow\left[\begin{matrix}x=3\\x=-2\end{matrix}\right.\)

Vậy x = 3 hoặc x = -2

g) |2x² - 3| - 4 = 11

|2x²- 3| = 11 + 4

|2x² - 3| = 15

\(\Rightarrow\left[\begin{matrix}2x^2-3=15\\2x^2-3=-15\end{matrix}\right.\Rightarrow\left[\begin{matrix}2x^2=18\\2x^2=-12\end{matrix}\right.\Rightarrow\left[\begin{matrix}x^2=9\\x^2=-6\end{matrix}\right.\Rightarrow\left[\begin{matrix}x^2=3^2\\\left(loại\right)\end{matrix}\right.\Rightarrow\left[\begin{matrix}x=3\\\end{matrix}\right.\)

Vậy x = 3.

Bài 1:

\((-48) . 72 +36 . (-304) \)

\(=\left[\left(-48\right).\left(36.2\right)\right]+36.\left(-340\right)\)

\(=\left[\left(-48\right).2\right].36+36.\left(-340\right)\)

\(=\left(-96\right).36+36.\left(-304\right)\)

\(=36.\left[\left(-96\right)+\left(-304\right)\right]\)

\(=36.\left(-400\right)\)

\(=-14400\)