\(F_A=P-F=18-10=8N\)

\(V=\dfrac{F_A}{d}=\dfrac{8}{10000}=8\cdot10^{-4}m^3\)

\(d=\dfrac{18}{8\cdot10^{-4}}=22500\)N/m³

\(F_A=P-P'=18-10=8N\)

\(V=\dfrac{F_A}{d}=\dfrac{8}{10000}=8\cdot10^{-4}m^3\)

\(d=\dfrac{P}{V}=\dfrac{18}{8\cdot10^{-4}}=22500\left(\dfrac{N}{m^2}\right)\)

Gọi d=ƯC(2n+7;5n+17)

\(\Rightarrow\left\{{}\begin{matrix}2n+7⋮d\\5n+17⋮d\end{matrix}\right.\)

\(\Rightarrow\left\{{}\begin{matrix}10n+35⋮d\\10n+34⋮d\end{matrix}\right.\)

\(\Rightarrow1⋮d\Rightarrow d=1\)

\(\Rightarrow\) phân số \(\dfrac{2n+7}{5n+17}\) tối giản

\(2A=\dfrac{4}{1.5}+\dfrac{6}{5.11}+\dfrac{8}{11.19}+\dfrac{10}{19.29}+\dfrac{12}{29.41}\)

\(2A=1-\dfrac{1}{5}+\dfrac{1}{5}-\dfrac{1}{11}+\dfrac{1}{11}-\dfrac{1}{19}+\dfrac{1}{19}-\dfrac{1}{29}+\dfrac{1}{29}-\dfrac{1}{41}\)

\(2A=1-\dfrac{1}{41}=\dfrac{40}{41}\)

\(A=\dfrac{40}{41}:2=\dfrac{20}{41}\)

\(3B=\dfrac{3}{1.4}+\dfrac{6}{4.10}+\dfrac{9}{10.19}+\dfrac{12}{19.31}\)

\(3B=1-\dfrac{1}{4}+\dfrac{1}{4}-\dfrac{1}{10}+\dfrac{1}{10}-\dfrac{1}{19}+\dfrac{1}{19}-\dfrac{1}{31}\)

\(3B=1-\dfrac{1}{31}=\dfrac{30}{31}\)

\(B=\dfrac{30}{31}:3=\dfrac{10}{31}\)

bn ơi bài 7 mk chẳng thấy tia Cz nằm đâu cả

Bài 1:

a. 

$545,26+117,3=662,56$

b.

$400,56-184,48=216,08$

c.

$4,21\times 3,2=13,472$

d.

$28,5:2,5=11,4$

Bài 2:

a. 2km 21 m = 2,021 km

b. 1020 kg = 1 tấn 20 kg 

c. 22 dam² 10 m² = 2210 m²

d. 90 giây = 1,5 phút

Bài 3:

a. Chiều rộng mảnh vườn:

$80:(3+2)\times 2=32$ (m)

Chiều rài mảnh vườn:

$80-32=48$ (m)

Diện tích mảnh vườn: 

$32\times 48=1536$ (m²)

b.

Diện tích lối đi chiếm số % diện tích mảnh vườn là:
$100-80=20$ (%)

Diện tích lối đi là:

$1536\times 20:100=307,2$ (m²)

1 Yesterday was cooler than today

2 Salim is the most beautiful in her team

3 His house is the highest in my city

4 No one in her class is as intelligent as Lan

5 BJ is one of the greatest tennis players in the world

1. Yesterday was colder than today.

2. Salim is the most beautiful in her team.

3. His house is the highest house in my city.

4.No one in her class is more intelligent than Lan

8. BJ isthe greatest tennis player in the world.

1) Yesterday was colder than today.

2) Salim is the most beautiful in her team.

3) His house is the highest house in my city.

4) No one in my class is more intelligent than Lan.

5) BJ is one of the greatest tennis players in the world.

\(B=2+2^2+2^3+2^4+...+2^{99}+2^{100}=2\left(1+2^2+2^3+2^4\right)+...+2^{96}\left(1+2^2+2^3+2^4\right)=2.31+2^6.31+...+2^{96}.31=31\left(2+2^6+...+2^{96}\right)⋮31\)

B=2+22+23+24+...+299+2100=2(1+22+23+24)+...+296(1+22+23+24)=2.31+26.31+...+296.31=31(2+26+...+296)⋮31

a b c a

D A B A 

c a a c

14 C

15 A

16 A

17 C

18 A

đây nha bn

14 c

15 a

16 a

17 c