`(x+1)+(x+2)+(x+3)+...+(x+9)=945`

`x+1+x+2+x+3+...+x+9=945`

`9x+(1+9)+(2+8)+(3+7)+(4+6)+5=945`

`9x+10+10+10+10+5=945`

`9x+45=945`

`9x=945-45`

`9x=900`

`x=900:9`

`x=100`

ta thấy có 10 cái ngoặc =>có 10 x

ta có: 

(x+x+x+x+....+x) +(1+5+9+13+...+37)=210(có 10 x)

x*10+190=210

x*10=30

x=3

k cho mk nha!

X= 2,7,8,27 nhé bạn

Duyệt nha

a) 17-x*2=13
=)-x*2=13-17
=)-x*2=-4
=)-x=-4:2
=)-x=-2
=)x=2
va nha

=9( 1/4.5+1/5.6+...+1/36.37)

=9( 1/4-1/37)... tự yinhs nha

tìm x : 

200 -(2 . x + 6) = 64 

2 . x + 6 = 200 - 64 

2 . x + 6 = 136 

2 . x = 136 - 6 

2 . x = 130 

x = 130 : 2 = 65 

Tính nhanh

1972 - (368 +972)

1972 -  1340 

= 632 

3345 - 1000 : 192  - 2 . (221 - 218 ) . 3

3345 - ( 1000 ko chia hết cho 192 ) 

999 + 85 = 1084 

( 1 + 37) x 37 : 2 = 703 

( 1 + 2017) x 2017 : 2 = 2035153

\(\dfrac{9+x}{13-x}=\dfrac{5}{6}\\ \Rightarrow5\left(13-x\right)=6\left(9+x\right)\\ \Rightarrow65-5x=54+6x\\ \Rightarrow6x+5x=65-54\\ \Rightarrow11x=11\\ \Rightarrow x=1\)

Vậy x = 1

ĐKXĐ: \(x\ne13\)

\(\dfrac{9+x}{13-x}=\dfrac{5}{6}\)

\(\Leftrightarrow\dfrac{6\left(9+x\right)}{6\left(13-x\right)}=\dfrac{5\left(13-x\right)}{6\left(13-x\right)}\)

\(\Rightarrow6\left(9+x\right)=5\left(13-x\right)\)

\(\Leftrightarrow54+6x=65-5x\)

\(\Leftrightarrow6x+5x=65-54\)

\(\Leftrightarrow11x=11\)

\(\Leftrightarrow x=1\) (thỏa mãn ĐKXĐ)

( x + 1 ) + ( x + 3 ) + ( x + 5 ) + ( x + 7 ) + ( x + 9 ) + ( x + 11 ) + ( x + 13 ) = 119

( x + x + x + x + x + x + x ) + ( 1 + 3 + 5 + 7 + 9 + 11 + 13 ) = 119

7x +  49 = 119

7x = 119 - 49

7x = 70

  x = 70 : 7

  x =    10

x=10 nha bạn.kick và kb với mình rồi mình gửi lời giải cho

\(9+\frac{x}{13}-x=\frac{5}{6}\)

\(\Leftrightarrow\frac{x}{13}-x=\frac{5}{6}-9\)

\(\Leftrightarrow x\left(\frac{1}{13}-1\right)=\frac{5}{6}-\frac{54}{6}\)

\(\Leftrightarrow\frac{-12}{13}x=\frac{-50}{6}\)

\(\Leftrightarrow x=\frac{-50}{6}\div\frac{-12}{13}\)

\(\Leftrightarrow x=\frac{50}{6}\times\frac{13}{12}\)

\(\Leftrightarrow x=\frac{650}{72}=\frac{325}{36}\)

\(9+\frac{x}{13}-x=\frac{5}{6}\)

\(\Rightarrow9+\frac{x}{13}-\frac{13x}{13}=\frac{5}{6}\)

\(\Rightarrow9+\frac{x-13x}{13}=\frac{5}{6}\)

\(\Rightarrow\frac{x-13x}{13}=\frac{5}{6}-9\)

\(\Rightarrow\frac{x-13x}{13}=-\frac{49}{6}\)

\(\Rightarrow x-13x=-\frac{49}{6}\cdot13=-\frac{637}{6}\)

\(\Rightarrow-12x=-\frac{637}{6}\)

\(\Rightarrow x=-\frac{637}{6}:(-12)=\frac{637}{72}\)

\(\frac{9+x}{13-x}=\frac{5}{6}\)

\(\Leftrightarrow6\left(9+x\right)=5\left(13-x\right)\)

\(\Leftrightarrow54+6x=65-5x\)

\(\Leftrightarrow54-65=-5x-6x\)

\(\Leftrightarrow-11=-11x\)

\(\Leftrightarrow x=\frac{11}{11}\)

\(\Leftrightarrow x=1\)

\(\frac{9+x}{13-x}=\frac{5}{6}\)

\(\Rightarrow\text{ }6\left(9+x\right)=5\left(13-x\right)\)

\(\Rightarrow\text{ }54+6x=65-5x\)

\(\Rightarrow\text{ }54-65=-5x-6x\)

\(\Rightarrow\text{ }-11=-11x\)

\(\Rightarrow\text{ }x=-11\text{ : }\left(-11\right)\)

\(\Rightarrow\text{ }x=1\)