Đáp án:
$\rm\#Japanese$
a) `3 5/7+x=5 3/14`
`=>3 10/14+x=4 17/14`
`=>x=4 17/14-3 10/14`
`=>x=1 1/2`
`=>x=3/2`
Vậy `x=3/2`.
b) `4/5x=2/15`
`=>x=2/15:4/5`
`=>x=1/6`
Vậy `x=1/6`.
c) `1/3+2/3x=3/4`
`=>2/3x=3/4-1/3`
`=>2/3x=5/12`
`=>x=5/8`
Vậy `x=5/8`.
d) `2 1/4xx(x-7 1/3)=3/2`
`=>x- 7 1/3=3/2: 2 1/4`
`=>x-7 1/3=3/2:9/4`
`=>x- 7 1/3=2/3`
`=>x=2/3+7 1/3`
`=>x=(2/3+1/3)+7`
`=>x=1+7`
`=>x=8`
Vậy `x=8`.
e) `1/4x+2/5+1 3/4x=3 2/5`
`=>x xx(1 3/4+1/4)=3 2/5-2/5`
`=>x xx(1+1)=3-0`
`=>x xx2=3`
`=>x=3/2`
Vậy `x=3/2`.
g) `x:3+x:2+1/5x=31/15`
`=>x xx1/3+x xx1/2+ x xx1/5=31/15`
`=>x xx(1/3+1/2+1/5)=31/15`
`=>x xx31/30=31/15`
`=>x=31/15:31/30`
`=>x=2`
Vậy `x=2`.
h) `1/(1xx2)+1/(2xx3)+1/(3xx4)+...+1/(x xx(x+1))=99/100`
`=>1-1/2+1/2-1/3+1/3-1/4+...+1/x-1/(x+1)=99/100`
`=>1-1/(x+1)=99/100`
`=>1/(x+1)=1-99/100`
`=>1/(x+1)=1/100`
`=>x+1=100`
`=>x=100-1`
`=>x=99`
Vậy `x=99`.
