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Câu 1a:
75% - 1 1/2 + 0,5 : 5/12 - (-1/2)^2
= 0,75 - 1,5 + 0,5 x 12/5 - 0,25
= (0,75 - 0,25) - 1,5 + 1,2
= 0,5 - 1,5 + 1,2
= - 1 + 1,2
= 0,2
Bài 1b:
(5/7.0,6 - 5: 3 1/2). (40% - 1,4).(-2)^3
= (3/7 - 5 x 2/7).(0,4 - 1,4).8
= - 1.(-1).8
= 8
a) 219 - 7(x + 1) = 100 <=> 7(x+1) = 219 - 100
<=> 7(x+1) = 119 <=> x + 1 = 119 : 7 <=> x + 1 = 17
b) (3x - 6).3 = 3434 <=> 3x - 6 = 3434 : 3 <=> 3x - 6 = 3333
<=> 3x = 27 + 6 <=> 3x = 33 <=> x = 11
a) 219−7(x+1)=100
- 7(x+ 1)= 100 - 219
- 7(x+ 1)= - 119
x+1 = -119 : (-7)
x+1 = 17
x= 17-1
x= 16
b) (3x - 6). 3 = 34
(3x - 6). 3 = 81
(3x - 6)= 81: 3
(3x - 6)= 27
3x= 27+ 6
3x= 33
x= 33:3
x= 11
b) (3x−6).3=34
Tìm số tự nhiên \(x\) , biết :
a) \(123-5\left(x+4\right)=38\)
b) \(\left(3.x-2^4\right).7^3=2.7^4\)
a) \(123-5\left(x+4\right)=38\)
\(5\left(x+4\right)=123-38\)
\(5\left(x+4\right)=85\)
\(x+4=85:5\)
\(x+4=17\)
\(x=17-4\)
\(x=13\)
Vậy \(x=13\).
b) \(\left(3x-2^4\right)\cdot7^3=2\cdot7^4\)
\(3x-16=2\cdot7^4:7^3\)
\(3x-16=2\cdot7\)
\(3x-16=14\)
\(3x=14+16\)
\(3x=30\)
\(x=30:3\)
\(x=10\)
Vậy \(x=10\).
a ) Ta có : 4(x - 5) - 3(x + 7) = -19
<=> 4x - 20 - 3x - 21 = -19
=> x - 41 = -19
=> x = -19 + 41
=> x = 22
b) Ta có " 7(x - 3) - 5(3 - x) = 11x - 5
<=> 7x - 21 - 15 + 5x = 11x - 5
<=> 12x - 36 = 11x - 5
=> 12x - 11x = -5 + 36
=> x = 31
a, \(70-5.\left(x-3\right)=45\\ =>5.\left(x-3\right)=70-45=25\\ =>x-3=25:5=5\\ =>x=5+3=8\)
b, \(10+2.x=4^5:4^3\\ =>2.x=\left(4^5:4^3\right)-10=16-10=6\\ =>x=6:2=3\)
a, 70 - 5 . ( \(x\) - 3) = 45
5 . ( \(x\)-3) = 70 - 45
5 . ( \(x\) - 3) = 25
\(x\) - 3 = 25: 5
\(x\) - 3 = 5
\(x\) = 5 + 3
\(x\) = 8
Vậy \(x\) = 8
b, 10 + 2 .\(x\) = \(4^5:4^3\)
10 + 2 . \(x\) = 1024 : 64
10 + 2 .\(x\) = 16
2 .\(x\) = 16 - 10
2 . \(x\) = 6
\(x\) = 6 : 2
\(x\) = 3
Vậy \(x\) = 3
Chúc bạn học tốt !!! 
a) \(2\left(x-5\right)-3\left(x+7\right)=14\)
\(\Leftrightarrow2x-10-3x-21=14\)
\(\Leftrightarrow-x-31=14\)
\(\Leftrightarrow-x=45\Leftrightarrow x=-45\)
b) \(5\left(x-6\right)-2\left(x+3\right)=12\)
\(\Leftrightarrow5x-30-2x-6=12\)
\(\Leftrightarrow3x-36=12\)
\(\Leftrightarrow3x=48\Leftrightarrow x=16\)
c) \(3\left(x-4\right)-\left(8-x\right)=12\)
\(\Leftrightarrow3x-12-8+x=12\)
\(\Leftrightarrow4x-20=12\)
\(\Leftrightarrow4x=32\Leftrightarrow x=8\)
d) \(-7\left(3x-5\right)+2\left(7x-14\right)=28\)
\(\Leftrightarrow-21x+35+14x-28=28\)
\(\Leftrightarrow-7x+35=0\Leftrightarrow x=5\)
\(\left(x+5\right)^4=\left(x+5\right)^6\)
\(\Rightarrow\left(x+5\right)^4-\left(x+5\right)^6=0\)
\(\Rightarrow\left(x+5\right)-\left(x+5\right)^2=0\)
\(\Rightarrow\)\(x=-4\)
Câu 2 : không có yêu cầu đề bài thì làm kiểu gì?
\(\left(x+5\right)^4=\left(x+5\right)^6\)
\(\Rightarrow\left(x+5\right)^6-\left(x+5\right)^4=0\)
\(\Rightarrow\left(x+5\right)^4.\left[\left(x+5\right)^2-1\right]=0\)
\(\Rightarrow\left(x+5\right)^4=0\)hoặc \(\left(x+5\right)^2-1=0\)
=> x + 5 = 0 hoặc (x + 5)2 = 1
=> x + 5 = 0 hoặc x + 5 = 1 hoặc x + 5 = -1
=> x = -5 hoặc x = -4 hoặc x = -6
câu 2 là cho A ....
\(\left(x+5\right)^4=\left(x+5\right)^6\)
\(\left(x+5\right)^6-\left(x+5\right)^4=0\)
\(\left(x+5\right)^4.\left[\left(x+5\right)^2-1\right]=0\)
\(\Rightarrow\orbr{\begin{cases}\left(x+5\right)^4=0\\\left(x+5\right)^2-1=0\end{cases}\Leftrightarrow\orbr{\begin{cases}x=-5\\x=-4\end{cases}}}\)
Vậy \(\orbr{\begin{cases}x=-5\\x=-4\end{cases}}\)
Sửa đề chút:
a)\(A=3+3^2+3^3+...+3^{100}\)
\(3A=3^2+3^3+3^4+...+3^{101}\)
\(3A-A=\left(3^2+3^3+...+3^{101}\right)-\left(3+3^2+...+3^{100}\right)\)
\(2A=3^{101}-3\)
\(A=\frac{3^{101}-3}{2}\)
b) Ta có: \(2A+3=3^n\)
\(\Rightarrow2.\left(\frac{3^{101}-3}{2}\right)+3=3^n\)
\(3^{101}-3+3=3^n\)
\(3^{101}=3^n\)
\(\Rightarrow n=101\)
Vậy \(n=101\)
Tham khảo nhé~