Orthocenter lies on the line `x +y = 2`
Let orthocenter be `O(alpha,3 -alpha)`
`BO _|_ AC`
`rArr (y-7)/(x-4) (alpha)/(1-alpha) =-1`
`rArr (alpha-1)/(alpha) =(y-7)/(x-4)`
`rArr 1-(1)/(alpha)=(y-7)/(x-4)`
`rArr (1)/(alpha)=1-(y-7)/(x-4)`
`rArr alpha =(x-4)/(x-y+3)`
Also, `AO _|_ BC`
`rArr (y-3+alpha)/(x-alpha) xx (4)/(3) =-1`
`rArr 4y =12 +4alpha =-3x +3 alpha`
`rArr alpha =-3x - 4y +12`
`:.` The locus is `(x-4)/(x-y+3) =- 3x -4y +12`