d,
`(5x-1)(2-x)+5x(x-6)=7`
`<=>10x-5x^2-2+x+5x^2-30x-7=0`
`<=>(-5x^2+5x^2)+(10x+x-30x)+(-2-7)=0`
`<=>-19x-9=0`
`<=>-19x=9`
`<=>x=-9/19`
Vậy `S={-9/19}`
e,
`(5/2x-2)(3/2x-1)-5/2x(x-3)=0`
`<=>15/4x^2-5/2x-3x+2-5/2x^2+15/2x=0`
`<=>(15/4x^2-5/2x^2)+(-5/2x-3x+15/2x)+2=0`
`<=>5/4x^2+2x+2=0`
`<=>5/4(x^2+8/5x+8/5)=0`
`<=>x^2+8/5x+8/5=0`
`<=>x^2+2 . x . 4/5+16/25+24/25=0`
`<=>(x+4/5)^2=-24/25` ( vô lí vì `(x+4/5)^2>=0 \ , \ ∀x` )
Vậy phương trình đã cho vô nghiệm
