Đáp án:
`a,` `x=-131/130`
`b,` `x=7/2`
`c,` `x=17/6`
`d,` `x=-13/12`
`e,` `x=-8`
`f,` `x=5/2`
Giải thích các bước giải:
`a,` `x+30%x=-1,31`
`⇔` `(1+30%).x=-1,31`
`⇔` `1,3.x=-1,31`
`⇔` `x=(-1,31)/(1,3)`
`⇔` `x=-131/130`
Vậy `x=-131/130`
`b,` `(x-1/2):1/3+5/7=9 5/7`
`⇔` `(x-1/2):1/3=9 5/7-5/7`
`⇔` `(x-1/2):1/3=9`
`⇔` `(x-1/2)=9 . 1/3`
`⇔` `x-1/2=3`
`⇔` `x=3+1/2`
`⇔` `x=7/2`
Vậy `x=7/2`
`c,` `1/2x-3/4=14/9. 3/7`
`⇔` `1/2x-3/4=2/3`
`⇔` `1/2x=2/3+3/4`
`⇔` `1/2x=17/12`
`⇔` `x=17/12 : 1/2`
`⇔` `x=17/6`
Vậy `x=17/6`
`d,` `-5/6-x=7/12+(-1)/3`
`⇔` `-5/6-x=1/4`
`⇔` `x=-5/6-1/4`
`⇔` `x=-13/12`
Vậy `x=-13/12`
`e,` `(x+3)/(-15)=1/3`
`⇒` `3(x+3)=-15`
`⇔` `3x+9=-15`
`⇔` `3x=-15-9`
`⇔` `3x=-24`
`⇔` `x=-24:3`
`⇔` `x=-8`
Vậy `x=-8`
`f,` `(4,5-2x)(-1 4/7)=11/14`
`⇔` `(4,5-2x)=11/14:(-1 4/7)`
`⇔` `4,5-2x=-1/2`
`⇔` `2x=4,5-(-1/2)`
`⇔` `2x=5`
`⇔` `x=5/2`
Vậy `x=5/2`
