Question

[Đỗ Khánh Linh]

Tìm x 

d)( x+1) +(x +4) +(x+7)+...+ (x+28)=155

e) (x+140): x + 260 =71+65x4

Answer 1

[Hồ Thu Giang]

(x+1)+(x+4)+(x+7)+....+(x+28)=155

x+x+x+...+x+(1+4+7+....+28) = 155

10x + 145 = 155

=> 10x = 155 - 145

=> 10x = 10

=> x = 10:10

=> x =1

Answer 2

[Thanh Tùng DZ]

a) (x + 1 ) + ( x + 4 ) + ( x + 7 ) + ... +  ( x + 28 ) = 155

( x + x + x + ... + x ) + ( 1 + 4 + 7 + ... + 28 ) = 155

10x + 145 = 145

10x = 155 - 145

10x = 10

=> x = 10 : 10

=> x = 1