x/2+x+x/3+x+x+x/4=23/4

⇒ 6x/12+12x/12+4x/12+12x/12+12x/12+3x/12=23/4

⇒ (6x+12x+4x+12x+12x+3x)/12=23/4

⇒ 49x/12=23/4

⇒ 49x=23/4.12

⇒ 49x=69

⇒ x=69/49

6x là sao bạn 

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

\(5x-3x=6\)

\(2x=6\)

\(x=3\)

5/3 x X - X =2

5/3 x X - X x1=2

(5/3-1) x X =2

2/3 x X =2

X=2:2/3

X=3

\(\frac{1}{3}+....+\frac{2}{x.\left(x+1\right)}=\frac{1999}{2001}\)

=>\(\frac{1}{2}.\left(\frac{1}{3}+...+\frac{2}{x.\left(x+1\right)}\right)=\frac{1999}{2001}.\frac{1}{2}\)

\(\Rightarrow\frac{1}{6}+\frac{1}{12}+...+\frac{1}{x.\left(x+1\right)}=\frac{1999}{4002}\)

\(\Rightarrow\frac{1}{2.3}+\frac{1}{3.4}+...+\frac{1}{x.\left(x+1\right)}=\frac{1999}{4002}\)

\(\Rightarrow\frac{1}{2}-\frac{1}{x+1}=\frac{1999}{4002}\)

\(\Rightarrow\frac{1}{x+1}=\frac{1}{2001}\)

=> x=2000

Tìm stn biết: 1/3 + 1/6 + 1/10 + ...+2/x(x+1)=1999/2001

Bài giải: Gọi x là số tự nhiên cần tìm

Cho S= 1/3 + 1/6 +1/10 +...+ 1/x(x+1)

\(\Rightarrow\)S= 2/6 + 2/12+ 2/20 +...+ 2/2[x(x+1)]

\(\Rightarrow\)1/2S= 1/2.3 + 1/3.4 + 1/ 4.5 +...+1/2[x(x+1)]

\(\Rightarrow\)1/2S=1/2-1/3+1/3-1/4+...+1/(x-1) .(x+1)

\(\Leftrightarrow\)1/2S=1/2-1/x+1

Vì S = 1999 / 2001\(\Rightarrow\)1/2S=1/2-1 . (x+1)=1999/2001-1998-2001=1/2001

\(\Rightarrow\)1/x+1=1/2001

\(\Leftrightarrow\)x+1=2001

         x =2001-1 =2000

Vậy số tự nhiên đó là: 2000

a) Ta có : ( x+3 ).( x- 5 ) = 0

suy ra: x+3 = 0 hoặc x - 5 = 0 

suy ra : x = -3 hoặc x = 5 

KL : Vậy x = -3 hoặc x = 5 

\(\left(x+1\right)^2+\left(x^2+1\right)=0\)

\(\Leftrightarrow\orbr{\begin{cases}\left(x+1\right)^2=0\\\left(x^2+1\right)=0\end{cases}\Leftrightarrow\orbr{\begin{cases}x+1=0\\x^2+1=0\end{cases}\Leftrightarrow}\orbr{\begin{cases}x=-1\\x^2=-1\end{cases}\Leftrightarrow}x=-1}\)

Vậy x=-1

tìm nghiệm hả????