`1`
`(3+4x)^2-8x(2x-1)=-20`
`⇔9+24x+16x^2-16x^2+8x+20=0`
`⇔(9+20)+(24x+8x)+(16x^2-16x^2)=0`
`⇔29+32x=0`
`⇔32x=-29`
`⇔x=-29/32`
Vậy `S={-29/32}`
`2`
`(x+3)^2-(x+2)^2=13`
`⇔x^2+6x+9-(x^2+4x+4)-13=0`
`⇔x^2+6x+9-x^2-4x-4-13=0`
`⇔(x^2-x^2)+(6x-4x)+(9-4-13)=0`
`⇔2x-8=0`
`⇔2x=8`
`⇔x=4`
Vậy `S={4}`
`3`
`(x+1)^2-(x+4)^2=20`
`⇔x^2+2x+1-(x^2+8x+16)-20=0`
`⇔x^2+2x+1-x^2-8x-16-20=0`
`⇔(x^2-x^2)+(2x-8x)+(1-16-20)=0`
`⇔-6x-35=0`
`⇔-6x=35`
`⇔x=-35/6`
Vậy `S={-35/6}`
`4`
`(2x+3)^2-(2x+5)^2=25`
`⇔4x^2+12x+9-(4x^2+20x+25)-25=0`
`⇔4x^2+12x+9-4x^2-20x-25-25=0`
`⇔(4x^2-4x^2)+(12x-20x)+(9-25-25)=0`
`⇔-8x-41=0`
`⇔-8x=41`
`⇔x=-41/8`
Vậy `S={-41/8}`
`5`
`(5+3x)^2-x(9x+3)=18`
`⇔25+30x+9x^2-9x^2-3x-18=0`
`⇔(25-18)+(30x-3x)+(9x^2-9x^2)=0`
`⇔7+27x=0`
`⇔27x=-7`
`⇔x=-7/(27)`
Vậy `S={-7/27}`
`6`
`(5x+1)^2-25(x+1)^2=50`
`⇔25x^2+10x+1-25(x^2+2x+1)-50=0`
`⇔25x^2+10x+1-25x^2-50x-25-50=0`
`⇔(25x^2-25x^2)+(10x-50x)+(1-25-50)=0`
`⇔-40x-74=0`
`⇔-40x=74`
`⇔x=-74/40`
`⇔x=-37/20`
Vậy `S={-37/20}`
