`a,|-5x|=3x-16`
Nếu `|-5x|=- 5x`
`<=>-5x≥0`
`<=>x≥0`
`| -5x|=5x`
`<=>-5x<0`
`<=> x< 0`
Khi `x ≥ 0` thì `|-5x| = 3x - 16`
`<=> -5x=3x-16`
`<=> -5x-3x=-16`
`<=> - 8x= -16`
`<=> x=2` `(TM)`
Khi `x<0` thì `|-5x| = 3x - 16`
`<=> 5x=3x-16`
`<=>5x-3x=-16`
`<=> 2x=-16`
`<=> x= - 8` `(TM)`
Vậy `S={ 2;-16}`
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