a) -5/2 - 1/2x = -19/5

1/2x=-5/2 - (-19/5)

1/2x=13/10

x=13/10:1/2

x=13/5

a)   

\(-2,5-0,5\cdot x=-3,8\)

\(0,5\cdot x=1,3\)

\(x=2,6\)

b) 

\(-5x-2^5=3x+2^3\)

\(-5x-3x=2^5+2^3\)

\(-8x=40\)

\(x=-20\)

c)

\(-1-\left|x\right|=-9\)

\(\left|x\right|=8\)

\(\Rightarrow x=8\) hoặc \(x=-8\)

K MK NHÉ!

Đặt tử A là T ta có:

5T=5(1+5+5²+...+5⁹)

5T=5+5²+...+5¹⁰

5T-T=(5+5²+...+5¹⁰)-(1+5+5²+...+5⁹)

T=(5¹⁰-1)/4

Mẫu A là H tính tương tự đc:(5⁹-1)/4.Thay vào ta có:\(A=\frac{\frac{5^{10}-1}{4}}{\frac{5^9-1}{4}}=\frac{5^{10}-1}{5^9-1}\)

B tính tương tự A được \(\frac{3^{10}-1}{3^9-1}\) tới đây sao nx

Ta có: \(A=5+5^2+5^3+...+5^{2019}\)

\(5A=5^2+5^3+5^4+...+5^{2020}\)

\(5A-A=5^{2020}-5\)

Hay \(4A=5^{2020}-5\)

+) Ta có: \(4A+5=5^{3x-2}\)

\(\Rightarrow\left(5^{2020}-5\right)+5=5^{3x-2}\)

\(\Rightarrow5^{2020}=5^{3x-2}\)

\(\Rightarrow3x-2=2020\)

\(\Rightarrow3x=2022\)

\(\Rightarrow x=674\)

Hok "tuốt" nha^^

\(x=\frac{2}{3}:\frac{-7}{5}\)

\(x=\frac{2}{3}.\frac{5}{-7}\)

\(x=\frac{2.5}{3.\left(-7\right)}\)

\(x=\frac{10}{-21}\)

-7/5.x = 2/3

x = 2/3 : -7/5

x = -10/21

\(8^x+2^{3x+1}=24\)

\(\left(2^3\right)^x+2^{3x}.2=24\)

\(2^{3x}+2^{3x}.2=24\)

\(2^{3x}.\left(1+2\right)=24\)

             \(2^{3x}.3=24\)

                 \(2^{3x}=24:3\)

                \(2^{3x}=8\)

=> 2^3x  = 2³

=>3x = 3

     x = 3 : 3

     x = 1

đúng ko

ủng hộ mk nha mọi người

\(\left(2x+\frac{3}{5}\right)^2-\frac{9}{25}=0\)

\(\Leftrightarrow\left(2x+\frac{3}{5}\right)^2=\frac{9}{25}\)

\(\Leftrightarrow\left(2x+\frac{3}{5}\right)^2=\left(\frac{3}{5}\right)^2\)

\(\Leftrightarrow\orbr{\begin{cases}2x+\frac{3}{5}=\frac{3}{5}\\2x+\frac{3}{5}=-\frac{3}{5}\end{cases}}\)

\(\Leftrightarrow\orbr{\begin{cases}2x=0\\2x=-\frac{6}{5}\end{cases}}\)

\(\Leftrightarrow\orbr{\begin{cases}x=0\\x=-\frac{3}{5}\end{cases}}\)

_Tần vũ_

\(3\left(3x-\frac{1}{2}\right)^3+\frac{1}{9}=0\)

\(\Leftrightarrow3\left(3x-\frac{1}{2}\right)^3=-\frac{1}{9}\)

\(\Leftrightarrow\left(3x-\frac{1}{2}\right)^3=-\frac{1}{27}\)

\(\Leftrightarrow\left(3x-\frac{1}{2}\right)^3=\left(-\frac{1}{3}\right)^3\)

\(\Leftrightarrow3x-\frac{1}{2}=\frac{-1}{3}\)

\(\Leftrightarrow3x=\frac{1}{6}\)

\(\Leftrightarrow x=\frac{1}{18}\)

_Tần Vũ_

a, ( 1999 + 313 ) - 1999

= 1999 - 1999 + 313

= 313

b, 364 - ( 364 - 111 )

= 364 - 364 - 111

= -111

c, 249 - ( 75- 51 )

= 249 - 24

= 225

a) ( 1999 + 313 ) - 1999

= 1999 + 313 - 1999

= ( 1999 - 1999 ) + 313

= 0 + 313

b) 364 - ( 364 - 111 )

= 364 - 364 + 111

= 0 + 111

= 111

c) 249 - 75 + 51

= 174 + 51 

= 225