Question

(x+1)+(x+2)+(x+3)+...(×+9)+(x+10)=1555

Answer 1

`(x+1)+(x+2)+(x+3)+...(x+9)+(x+10)=1555`

`x+1+x+2+x+3+...+x+9+x+10=1555`

`(x+x+x+....+x+x)+(1+2+3+...+9+10)=1555`

`10x + 55 =1555`

`10x = 1555-55 =1500`

`x = 1500/10 = 150`

Vậy `x=150`

Answer 2

<=>10x+55=1555

=>10x=1500

=>x=150

Answer 3

( x + 1) + ( x + 2 ) + ( x + 3 ) +...+ ( x + 10)= 1555

= 1555 - [x . 10 (vì mỗi ngoặc có 1 x nên có 10 ngoặc thì có 10 x) +10 + ( 9+ 1 ) + ( 8+ 2) + ( 7 + 3) + ( 6 + 4) + 5] = x . 10 + ( 10 . 5 + 5 )

x . 10 = 1555 - ( 10 . 5 + 5) = 1555 - 55 = 1500

x = 1500 : 10

x = 150