Question

[Thắng Nguyễn]

Tìm x biết: \(\left(\frac{1}{2\cdot5}+\frac{1}{5\cdot8}+\frac{1}{8\cdot11}+...+\frac{1}{65\cdot68}\right)x-\frac{7}{34}=\frac{19}{68}\)
 

Answer 1

[chelsea]

(1/2.5+1/5.8+......+1/65.68)x=19/68+7/34=33/68

(1/2.5+1/5.8+.......+1/65.68).x.3=33/68.3=99/68

(3/2.5+3/5.8=.......+3/65.68).x=99/68

(1/2-1/5+1/5-1/8+....-+1/65-1/68).x=99/68

(1/2-1/68).x=99/68

33/68.x=99/68

=>x=3

k cho mình nha