Bài 1:
`a)`
`(7x-3)/(x-1)=2/3` `(x\ne1)`
`<=>3(7x-3)=2(x-1)`
`<=>21x-9=2x-2`
`<=>21x-2x=-2+9`
`<=>19x=7`
`<=>x=7/19` (thoả mãn)
Vậy `S={7/19}`
$\\$
`b)`
`(2(3-7x))/(x+1)=1/2` `(x\ne-1)`
`<=>2.2(3-7x)=x+1`
`<=>12-28x=x+1`
`<=>-28x-x=1-12`
`<=>-29x=-11`
`<=>x=11/29` (thoả mãn)
Vậy `S={11/29}`
$\\$
`c)`
`1/(x-2)+3=(3-x)/(x-2)` `(x\ne2)`
`<=>(1+3(x-2))/(x-2)=(3-x)/(x-2)`
`=>1+3x-6=3-x`
`<=>-5+3x=3-x`
`<=>3x+x=3+5`
`<=>4x=8`
`<=>x=2` (không thoả mãn)
Vậy `S=∅`
$\\$
`d)`
`(8-x)/(x-7)-8=1/(x-7)` `(x\ne7)`
`<=>(8-x-8(x-7))/(x-7)=1/(x-7)`
`=>8-x-8x+56=1`
`<=>-9x+64=1`
`<=>-9x=-63`
`<=>x=7` (không thoả mãn)
Vậy `S=∅`
$\\$
Bài 2:
`a)`
`(x+5)/(x-5)-(x-5)/(x+5)=20/(x^2-25)` `(x\ne+-5)`
`<=>((x+5)^2-(x-5)^2)/(x^2-25)=20/(x^2-25)`
`=>x^2+10x+25-(x^2-10x+25)=20`
`<=>20x=20`
`<=>x=1` (thoả mãn)
Vậy `S={1}`
$\\$
`b)`
`1/(x-1)+2/(x+1)=x/(x^2-1)` `(x\ne+-1)`
`<=>(x+1+2(x-1))/(x^2-1)=x/(x^2-1)`
`=>x+1+2x-2=x`
`<=>3x-1=x`
`<=>2x=1`
`<=>x=1/2` (thoả mãn)
Vậy `S={1/2}`
