Question

Tìm x biết:

x/1.4+x/4.7+x/7.10+x/10.13+x/13.16=5/2

Answer 1

x/1.4+x/4.7+x/7.10+x/10.13+x/13.16=5/2

=>x/3(1/4-1/7+1/7-1/10+1/10-1/13+1/13-1/16)=5/2

=>x/3.(1/4-1/16)=5/2

=>x/3.3/16=5/2

=>x/3=5/2:3/16

=>x/3=40/3

=>x=40

Vậy x=40

Answer 2

x/1.4 + x/4.7 + x/7.10 + x/10.13 + x/13.16 = 5/6

=> x.1/3.(3/1.4 + 3/4.7 + 3/7.10 + 3/10.13 + 3/13.16) = 5/6

=> x.1/3.(1 - 1/4 + 1/4 - 1/7 + 1/7 - 1/10 + 1/10 - 1/13 + 1/13 - 1/16) = 5/6

=> x.1/3.(1 - 1/16) = 5/6

=> x.1/3.15/16 = 5/6

=> x.1/3 = 5/6 : 15/16

=> x.1/3 = 8/9

=> x = 8/9 : 1/3

=> x = 8/3