`***`Lời giải`***`
5)
`(2x+3)^2-4(x-1)^2=0`
`<=>(2x+3)^2-[2(x-1)]^2=0`
`<=>[2x+3+2(x-1)][2x+3-2(x-1)]=0`
`<=>(2x+3+2x-2)(2x+3-2x+2)=0`
`<=>5(4x+1)=0`
`<=>4x+1=0`
`<=>4x=-1`
`<=>x=-1/4`
Vậy `S={-1/4}`
7)
`(5x-1)(5x+1)=25x^2-7x+15`
`<=>25x^2-1=25x^2-7x+15`
`<=>25x^2+7x-25x^2=15+1`
`<=>7x=16`
`<=>x=16/7`
Vậy `S={16/7}`
9)
`(x+3)(4-x)+(x+1)(x-1)=10`
`<=>x(4-x)+3(4-x)+(x+1)(x-1)=10`
`<=>4x-x^2+12x-3x+x^2-1=10`
`<=>4x-x^2+12x-3x+x^2=10+1`
`<=>13x=11`
`<=>x=11/13`
Vậy `S={11/13}`
11)
`(x+1)^2-(x+2)(x-2)=0`
`<=>x^2+2x+1-(x^2-4)=0`
`<=>x^2+2x+1-x^2+4=0`
`<=>2x=-5`
`<=>x=-5/2`
Vậy `S={-5/2}`
