\(5^{x-1}+5^{x-2}+5^{x-3}=775\\ 5^{x-3}.\left(25+5+1\right)=775\\ 5^{x-3}.31=775\\ 5^{x-3}=\dfrac{775}{31}=25=5^2\\ x-3=2\\ x=5\)

Cảm ơn bn

\(5^x+5^{x+1}+5^{x+2}=775\)

\(\Leftrightarrow5^x.1+5^x.5+5^x.5^2=775\)

\(\Leftrightarrow5^x.\left(1+5+5^2\right)=775\)

\(\Leftrightarrow5^x.\left(1+5+25\right)=775\)

\(\Leftrightarrow5^x.31=775\)

\(\Rightarrow5^x=775:31=25=5^2\)

\(\Rightarrow x=2\)

Vậy \(x=2\)

5^x + 5^{x + 1} + 5^{x + 2} = 775

5^x . 1 + 5^x . 5 + 5^x . 25 = 775

5^x . (1 + 5 + 25) = 775

5^x . 31 = 775

5^x       = 775 : 31

5^x       = 25

5^x       = 5²

Suy ra : x = 2

      \(5^x+5^{x+1}+5^{x+2}=775\)

<=>\(5^x.\left(1+5+5^2\right)=775\)

<=>\(5^x.31=775\)

<=>\(5^x=775:31\)

<=>\(5^x=25\)=>\(x=2\)

dễ. k đi mình hứa sẽ làm cho

CÁC BẠN GIÚP MÌNH NHA

MAI MÌNH ĐI HỌC RỒI NHA

bài 2 tui ko làm đc 

A={245;250;255;260;....;770}

Tập hợp A có số p/tử là:

(770-245):5+1=106 p/tử

a, \(-5x-1-\dfrac{x}{2}+\dfrac{1}{3}=\dfrac{3}{2}x-5\Leftrightarrow-7x=-\dfrac{13}{3}\Leftrightarrow x=\dfrac{13}{21}\)

b, \(3x-\dfrac{3}{2}-5x-3=-x+\dfrac{1}{5}\Leftrightarrow-x=\dfrac{47}{10}\Leftrightarrow x=-\dfrac{47}{10}\)

a) \(\left(3x-1\right).\left(\frac{-1}{2}x+5\right)=0\)

\(\Rightarrow3x-1=0\Rightarrow3x=1\Rightarrow x=\frac{1}{3}\)

\(\frac{-1}{2}x+5=0\Rightarrow\frac{-1}{2}x=-5\Rightarrow x=10\)

b) \(3\left(x-\frac{1}{2}\right)-5\left(x+\frac{3}{5}\right)=x+\frac{1}{5}\)

\(3x-\frac{3}{2}-5x-3=x+\frac{1}{5}\)

\(\Rightarrow3x-5x-x=\frac{1}{5}+\frac{3}{2}+3\)

\(-3x=\frac{47}{10}\)

\(x=\frac{-47}{30}\)

c) \(-5.\left(x+\frac{1}{5}\right)-\frac{1}{2}\left(x-\frac{2}{3}\right)=\frac{3}{2}x-\frac{5}{6}\)

\(-5x-1-\frac{1}{2}x+\frac{1}{3}=\frac{3}{2}x-\frac{5}{6}\)

\(-5x-\frac{1}{2}x-\frac{3}{2}x=\frac{-5}{6}+1-\frac{1}{3}\)

\(-7x=\frac{-1}{6}\)

\(x=\frac{1}{42}\)

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

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

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

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

\(\Rightarrow3x-\frac{1}{2}=\frac{-1}{3}\)

\(3x=\frac{1}{6}\)

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

Học tốt nhé bn!
 

x = \(\frac{1}{18}\)nha