a, \(390-\left(x-7\right)=13^2:12\)

\(390-\left(x-7\right)=\) \(\dfrac{169}{12}\)

\(x-7=390-\dfrac{169}{12}\)

\(x-7=\dfrac{4511}{12}\)

\(x=\dfrac{4511}{12}+7\)

\(x=\dfrac{4595}{12}\)

Vậy ...

b, \(\left(x-35.2^2\right):7=3^3-24\)

\(\left(x-35.4\right):7=27-24\)

\(\left(x-140\right):7=3\)

\(\Leftrightarrow\left(x-140\right)=3.7\)

\(\Leftrightarrow x-140=21\)

\(\Leftrightarrow x=161\)

Vậy .....

c) \(x-6:2-\left(4^2.3-24\right):2:6=3\)

\(x-3-\left(16.3-24\right):2:6=3\)

\(x-3-\left(48-24\right):2:6=3\)

\(x-3-24:2:6=3\)

\(x-3-2=3\)

\(x=3+2+3\)

\(x=8\)

Vậy ......

d) \(4x-5=5+5^2+5^3+.....+5^{99}\)

Đặt :

\(A=5+5^2+.........+5^{99}\)

\(\Leftrightarrow5A=5^2+5^3+..........+5^{100}\)

\(\Leftrightarrow5A-A=\left(5^2+5^3+......+5^{100}\right)-\left(5+5^2+....+5^{99}\right)\)

\(\Leftrightarrow4A=5^{100}-5\)

\(\Leftrightarrow A=\dfrac{5^{100}-5}{4}\)

\(\Leftrightarrow4x+5=\dfrac{5^{100}-5}{4}\)

Đến đây thì sao nữa nhỉ ?

e) \(\left(2x-1\right)^4=625\)

\(\Leftrightarrow\left[{}\begin{matrix}\left(2x-1\right)^4=5\\\left(2x-1\right)^4=-5\end{matrix}\right.\)

\(\Leftrightarrow\left[{}\begin{matrix}2x-1=5\\2x-1=-5\end{matrix}\right.\)

\(\Leftrightarrow\left[{}\begin{matrix}x=3\\x=-2\end{matrix}\right.\)

Vậy ....

1 

a 

\(5\cdot\left(x-13\right)=20\)   

\(x-13=20:5\)   

\(x-13=4\)   

\(x=4+13\)   

\(x=17\)   

b 

\(26-3\cdot\left(x+4\right)=5\)  

\(3\cdot\left(x+4\right)=26-5\)   

\(3\cdot\left(x+4\right)=21\)   

\(x+4=21:3\)   

\(x+4=7\)   

\(x=7-4\)   

\(x=3\)   

c 

\(12x-5^4:5^2=35\)   

\(12x-5^2=35\)   

\(12x-25=35\)   

\(12x=35+25\)   

\(12x=60\)   

\(x=60:12\)   

\(x=5\)   

2 

\(2+4+6+...+58\)   

Số số hạng 

\(\left(58-2\right):2+1=29\)   

Tổng 

\(\left(58+2\right)\cdot29:2=870\)

a) 4.25-12.5+170:10

=100-60+17

=40+17

=57

b) (7+3³:3²).4-3

=(7+3).4-3

=10.4-3

=40-3

=37

c) 12:{400:[500-(125+25.7)]}

=12:{400:[500-(125+175)]}

=12:{400:[500-300]}

=12:{400:200}

=12:2

=6

d) 168+{[2.(2⁴+3²)-256⁰]:7²}

=168+{[2.(16+9)-1]:49}

=168+{[2.25-1]:49}

=168+{[50-1]:49}

=168+{49:49}

=168+1

=169

\(\left(x-13\right)=4^9:4^6\)

x-13 = \(4^3\)

x = 64 + 13

x = 77

a: \(7^{x-5}+121=58\cdot2^3\)

=>\(7^{x-5}+121=58\cdot8\)

=>\(7^{x-5}=343\)

=>x-5=3

=>x=8

b: \(10^{x+25}+168=73\cdot2^4\)

=>\(10^{x+25}+168=73\cdot16\)

=>\(10^{x+25}=1000\)

=>x+25=3

=>x=-22

c: \(5x+59=21\cdot2^2=21\cdot4=84\)

=>5x=84-59=25

=>x=5

d: \(3+2^{x-1}=24-\left[4^2-\left(2^2-1\right)\right]\)

=>\(2^{x-1}+3=24-16+3\)

=>\(2^{x-1}=8\)

=>x-1=3

=>x=4

7ˣ⁻⁵ + 121 = 58.2³

7ˣ⁻⁵ = 58.8 - 121

7ˣ⁻⁵ = 464 - 121

7ˣ⁻⁵ = 343

7ˣ⁻⁵ = 7³

x - 5 = 3

x = 3 + 5

x = 8

-------

10ˣ⁻²⁵ + 168 = 73.2⁴

10ˣ⁻²⁵ = 73.16 - 168

10ˣ⁻²⁵ = 1000

10ˣ⁻²⁵ = 10³

x - 25 = 3

x = 3 + 25

x = 28

-------- 

5x + 59 = 21.2²

5x = 21.4 - 59

5x = 84 - 59

5x = 25

x = 25 : 5

x = 5

--------

3 + 2ˣ⁻¹ = 24 - [4² - (2² - 1)]

3 + 2ˣ⁻¹ = 24 - (16 - 3)

2ˣ⁻¹ = 24 - 13 - 3

2ˣ⁻¹ = 8

2ˣ⁻¹ = 2³

2ˣ⁻¹ = 3

x - 1 = 3

x = 3 + 1

x = 4