`\text{~~Holi~~}`
`a.`
`((2x+1)^2)/5-((x-1)^2)/3=(7x^2-14x-5)/(15)`
`-> 3(2x+1)^2-5(x-1)^2=7x^2-14x-5`
`-> 3(4x^2+4x+1)-5(x^2-2x+1)=7x^2-14x-5`
`-> 12x^2+12x+3-5x^2+10x-5=7x^2-14x-5`
`-> 12x^2+12x+3-5x^2+10x=7x^2-14x`
`-> 7x^2+22x+3=7x^2-14x`
`-> 22x+14x=-3`
`-> 36x=-3`
`-> x=-1/(12)`
`\text{Vậy} S={-1/(12)}`
`b.`
`(7x-1)/6+2x=(16-x)/5`
`-> 5(7x-1)+60x=6(16-x)`
`-> 35x-5+60x=96-6x`
`-> 95x-5=96-6x`
`-> 95+6x=96+5`
`-> 101x=101`
`-> x=1`
`\text{Vậy} S={1}`
`c.`
`(x-2)^2/3-((2x-3)(2x+3))/8+((x-4)^2)/6=0`
`-> 8(x-2)^2-3(2x-3)+4(x-4)^2=0`
`-> 8(x^2-4x+4)-3(4x^2-9)+4(x^2-8x+16)=0`
`-> 8x^2-32x+32-12x^2+27+4x^2-32x+64=0`
`-> 0-64x+123=0`
`-> -64x+123=0`
`-> -64x=-123`
`-> x=(-123)/(-64)`
`-> x= (123)/(64)`
`\text{Vậy} S={(123)/(64)}`