`a. (x^2-x)/(2x)=0` (`x\ne0`)
`-> (x(x-1))/(2x)=0`
`-> x-1/2=0`
`-> x-1=0`
`-> x=1`
`b. ((x-1)(x+2))/(x^2-4x+3)=0` (`x\ne{1;3}`)
`-> ((x-1)(x+2))/((x-3)(x-1))=0`
`-> (x+2)/(x-3)=0`
`-> x+2=0`
`-> x=-2`
`c. (x^2-1)/(x^2-2x+1)=0`
`-> ((x-1)(x+1))/((x-1)^2)=0`
`-> (x+1)/(x-1)=0`
`-> x+1=0`
`-> x=1`