Equation of the conic is ,
`x^2-y^2-8x+2y+11=0`
Differentiating it with respect to `x`,
`2x-2ydy/dx-8+2dy/dx = 0`
`=>dy/dx(2-2y) = 8-2x`
`=>dy/dx = (4-x)/(1-y)`
At point `(2,1)`,
`dy/dx = oo`
`:.` slope is `oo`.
Now, equation of line,
`y = mx+c`
At point `(2,1)`,
`1 = 2m+c => c = 1-2m`
`:.` Equation of tangent,
`y = m(x)+(1-2m)`
`=>y = m(x-2)+1`
`=>(y-1)/m = (x-2)`
As `m = oo`,
`:. x-2 = 0`
`=>x=2`, which is the required equation.
