(6x5-x)^2=676

(30-x)^2=676

(30-x)^2=26^2

30-x=26

x=30-26

x=4

a, 1 + 3 + 5 + 7 + ............. + n 

=\(\frac{\left(n+1\right)\left(n-1\right)}{2}\)=676

=>\(\left(n+1\right)\left(n-1\right)\)=676*2 =1352

Còn lạ bạn tự suy luận là ra

[1+n].n:2=676

[1+n].n=1352=35.37

n=20

[2+n].n:2=992

[2+n].n=1984=42.44

n=44

mình giúp đc câu b thôi nha

b. x + (x+2) + (x+4) +...+ (x+50)=676 (26 số hạng)

= (x + x + x + x +.....+x) + (2 + 4 + 6 + ..... + 50) = 676 (26 x ; 25 số hạng)

= 26x + ( (50 + 2) * 25 : 2) = 676

= 26x + 650 = 676

26x = 676 - 650

26x = 26

x = 26 : 26

=> x = 1

Bạn tham khảo nhé!!!!!

a \(\dfrac{2}{3}x+\dfrac{1}{3}=\dfrac{1}{5}\\ \dfrac{2}{3}x=\dfrac{1}{5}-\dfrac{1}{3}\\ \dfrac{2}{3}x=\dfrac{-2}{15}\\ x=-\dfrac{2}{15}:\dfrac{2}{3}\\ x=-\dfrac{1}{5}\)   b) \(\dfrac{4}{5}-\dfrac{5}{3}x=-2\\ \dfrac{5}{3}x=\dfrac{4}{5}+2\\ \dfrac{5}{3}x=\dfrac{14}{5}\\ x=\dfrac{14}{5}:\dfrac{5}{3}\\ x=\dfrac{42}{25}\)c) \(\dfrac{1}{5}+\dfrac{5}{3}:x=\dfrac{1}{2}\\ \dfrac{5}{3}:x=\dfrac{1}{2}-\dfrac{1}{5}\\ \dfrac{5}{3}:x=\dfrac{3}{10}\\ x=\dfrac{5}{3}:\dfrac{3}{10}\\ x=\dfrac{50}{9}\)d) \(\dfrac{5}{7}:x-3=-\dfrac{2}{7}\\ \dfrac{5}{7}:x=3-\dfrac{2}{7}\\ \dfrac{5}{7}:x=\dfrac{19}{7}\\ x=\dfrac{5}{7}:\dfrac{19}{7}\\ x=\dfrac{5}{19}\)

Mơn

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