\(5x+2x=6^2-5^0\Leftrightarrow5x+2x=6^2-1\)

\(\Leftrightarrow5x-2x=36-1\Leftrightarrow5x-2x=35\Leftrightarrow x\left(5+2\right)=35\)

\(\Leftrightarrow7x=35\Leftrightarrow x=35:7\Leftrightarrow x=5\)

\(5x+x=150:2+3\Leftrightarrow5x+x=75+3\)

\(\Leftrightarrow5x+x=78\Leftrightarrow x\left(5+1\right)=78\Leftrightarrow x6=78\)

\(\Leftrightarrow x=78:6\Leftrightarrow x=13\)

a) 5x + 2x = 6² - 5⁰

7x = 35 => x = 5

b) 5x + x = 150 : 2 + 3

6x = 78 => x = 13

c) 6x + x = 5¹¹ : 5⁹ + 3¹

7x = 28 => x = 4

d) 5x + 3x = 3⁶ : 3³ x 4 + 12

8x = 120 => x = 15

e) 4x + 2x = 68 - 2¹⁹ : 2¹⁶

6x = 60 => x = 10

f) 5x + x = 39 - 3¹¹ : 3⁹

6x = 30 => x = 5

g) 7x - x = 5²¹ : 5¹⁹ + 3 x 2² - 7⁰ 

6x = 36 => x = 6

h) 7x - 2x = 6¹⁷ : 6¹⁵ + 44 : 11

5x = 40 => x = 8

gọi d là ƯC(8a+3 ;5a+2)

Ta có:8a+3 chia hết cho d ; 5a+2 chia hết cho d

Nên 8a+3-5a+2

=> 2(8a+3)-3(5a+2) chia hết cho d

 => 1 chia hết cho d

Vậy d=1 nên 8a+3 và 5a+2 là hai số nguyên tố cùng nhau

Gọi d là ƯC_{(8a + 3; 5a + 2)} 

Ta có 8a + 3 \(⋮\)d; 5a + 2 \(⋮\)d

Nên (8a + 3) - (5a + 2)

=> 2.(8a + 3) - 3.(5a + 2) \(⋮\)d 

= 1 \(⋮\)d => d = 1

Vì d = 1 => 8a + 5 và 5a + 2 là hai số nguyên tố cùng nhau.

ta có :

 a - 1 \(\in\) BC( 2 , 3 , 4 , 5 , 6 ) \(\Rightarrow\) a - 1 \(\in\) { 60 , 120 , 180 , 240 , 300 , 360 }

Do a \(⋮\) 7 nên a = 301

                 vậy , ta tìm được a = 301

Tham khảo nhé:

To: cococococococococo@yahoo.com

Subject: My house

Hi Phong,

Thanks for your e-mail. Now I'll tell you about my house. I live with my parents and my brother in a city house. It's not so big but it's very comfortable. There are five rooms: a living room, a kitchen, a bedroom, a bathroom and hall. I my bedroom best. What about you? Where do you live? Tell me in your next e-mail.

Best wishes,

Duc

Hi...., my name is.....
How are you? I'm very happy now. Are you happy now? Now I will tell you about your beautiful house. Outside the house is the flower garden and old trees are old.The house has a washing machine, refrigerator and robots, and they are wonderful! And next, I will tell you about your friends line, they are very funny!! So I love this life very much. Goodbye and see you in the next letter offline!

a) x*(1+2+3+...+20)=2100

                   x*210 =2100

                   x        =10

dấu * là nhân hả bạn

\(8x+2x=25\cdot2^2\Leftrightarrow8x+2x=25\cdot4\)

\(\Leftrightarrow8x+2x=100\Leftrightarrow x\left(8+2\right)=100\)

\(\Leftrightarrow x\cdot10=100\Leftrightarrow\orbr{\begin{cases}x=100:10\\x\cdot10=10\cdot10\end{cases}}\)

\(\Leftrightarrow x=10\)

Vậy giá trị x cần tìm để thỏa mãn yêu cầu của đề bài là \(x=10\)

8x + 2x = 25 . 4

10x = 100

=> x = 100 : 10 = 10

1) \(3\left(5x-2\right)-9=6\)

\(15x-6=6+9\)

\(15x=15+6\)

\(15x=21\)

\(x=\frac{7}{5}\)

2) \(4\left(3x-2\right)+7\left(3x-2\right)=22\)

\(\left(3x-2\right)\left(4+7\right)=22\)

\(\left(3x-2\right)\cdot11=22\)

\(\left(3x-2\right)=2\)

\(3x=4\)

\(x=\frac{4}{3}\)

3) \(2x^2-6x=0\)

\(2x\left(x-3\right)=0\)

\(\Rightarrow\orbr{\begin{cases}2x=0\\x-3=0\end{cases}}\)

\(\Rightarrow\orbr{\begin{cases}x=0\\x=3\end{cases}}\)

Vậy,............

\(1)3\left(5x-1\right)-9=6\)

\(\Rightarrow3\left(5x-2\right)=15\)

\(\Rightarrow5x-2=5\Rightarrow5x=7\Rightarrow x=\frac{7}{5}\)

\(2)4\left(3x-2\right)+7\left(3x-2\right)=22\)

\(\Rightarrow11\left(3x-2\right)=22\)

\(\Rightarrow33x-22=22\Rightarrow33x=44\Rightarrow x=\frac{4}{3}\)

\(3)2x^2-6x=0\)

\(\Rightarrow2x\left(x-2\right)=0\)

\(\Rightarrow\orbr{\begin{cases}2x=0\\x-2=0\end{cases}}\Rightarrow\orbr{\begin{cases}x=0\\x=2\end{cases}}\)

\(2^2\cdot2^2\)

\(=2^{2+2}\)

\(=2^4\)

2² x 2² = 16

18.1+4+7+10+13+16+19+....+97+100

=18+(4+7+10+13+16+19+....+97+100)

Ta có:4+7+10+13+16+19+....+97+100

Số số hạng là:

(100-4):3+1=32(số hạng)

Tổng là:

(100+4).32:2=1664

=>18+1664

=1682

18.1+4+7+10+13+16+19+....+97+100

=18+(4+7+10+13+16+19+....+97+100)

Ta có:4+7+10+13+16+19+....+97+100

Số số hạng là:

(100-4):3+1=32(số hạng)

Tổng là:

(100+4).32:2=1664

=>18+1664

=1682