
Solve line PQ & QR Point Q(m−11−c,m−11−c+1)
m2H=m−11−c−3m−11−c+2=1−c−3m+31−c+2m−2=−41
m2H=m−11−c−3m−11−c+2=1−c−3 m+31−c+2 m−2=−41...(1)
∵mPH=05→∞
⇒ Slope of line QR (m) =0
Put value of m in equation (1)
1−c+31−c−2=−41⇒c=0
so m−c=0 Ans.