Đáp án+Giải thích các bước giải:
Bài 1:
`a) (-3)/5:2/7+``(-3)/5.``5/7+2``3/5`
`=(-3)/5. 7/2 + (-3)/5.``5/7+13/5`
`=(-3)/5(7/2+5/7)+13/5`
`=(-3)/5 . 59/14+13/5`
`=(-177)/70+13/5`
`=1/14`
`b) ((-2)/3)^2 - 3/10. (4/9+3/7)`
`=4/9-3/10.``55/63`
`=4/9-11/42`
`=23/126`
Bài 2:
`a) 2``5/7+8/5:x=6``1/7`
`=> 19/7+8/5:x=43/7`
`=> 8/5:x=43/7 -19/7`
`=>8/5:x=24/7`
`=>x=7/15`
`b) |3x+1/4|=7/12`
`=>` \(\left[ \begin{array}{l}3x+\frac{1}{4}=\frac{7}{12}\\3x+\frac{1}{4}=\frac{-7}{12}\end{array} \right.\)
`<=>` \(\left[ \begin{array}{l}3x=\frac{1}{3}\\3x=\frac{-5}{6}\end{array} \right.\)
`<=>` \(\left[ \begin{array}{l}x=\frac{1}{9}\\x=\frac{-5}{18}\end{array} \right.\)
`=>`
`x` $\in$ `{1/9;-5/18}`
$@helenavalerie$
