When given polynomial is divisible by another polynomial then remainder is x+a.
It means, coefficient of x must be 1 and constant term is a.
`therefore 2k-9=1 " and" k^(2)-8k+10=a`
`implies k=5 `
`therefore (5)^(2)-8(5)+10=a implies a= -5`
`therefore k=5 " and" a=-5`