first off, let's find the slope of PQ
![\bf \begin{array}{ccccccccc} &&x_1&&y_1&&x_2&&y_2\\ % (a,b) &P&(~ 2 &,& 2~) % (c,d) &Q&(~ 8 &,& 4~) \end{array} \\\\\\ % slope = m slope = m\implies \cfrac{\stackrel{rise}{ y_2- y_1}}{\stackrel{run}{ x_2- x_1}}\implies \cfrac{8-2}{4-2}\implies \cfrac{6}{2}\implies 3]()
now, a perpendicular line to PQ, will have a negative reciprocal slope, thus
now, we also know that, the line is a bisector of PQ, therefore, it cuts PQ in two equal halves, so it passes half-way through PQ, what is that point anyway?
![\bf ~~~~~~~~~~~~\textit{middle point of 2 points }\\\\ \begin{array}{ccccccccc} &&x_1&&y_1&&x_2&&y_2\\ % (a,b) &P&(~ 2 &,& 2~) % (c,d) &Q&(~ 8 &,& 4~) \end{array}\qquad % coordinates of midpoint \left(\cfrac{ x_2 + x_1}{2}\quad ,\quad \cfrac{ y_2 + y_1}{2} \right) \\\\\\ \left( \cfrac{8+2}{2}~~,~~\cfrac{4+2}{2} \right)\implies (5~,~3)]()
so then, what's the equation of a line whose slope is -1/3 and runs through 5,3?
![\bf \begin{array}{ccccccccc} &&x_1&&y_1\\ % (a,b) &&(~ 5 &,& 3~) \end{array} \\\\\\ % slope = m slope = m\implies -\cfrac{1}{3} \\\\\\ % point-slope intercept \stackrel{\textit{point-slope form}}{y- y_1= m(x- x_1)}\implies y-3=-\cfrac{1}{3}(x-5) \implies y-3=-\cfrac{1}{3}x+\cfrac{5}{3} \\\\\\ y=-\cfrac{1}{3}x+\cfrac{5}{3}+3\implies y=-\cfrac{1}{3}x+\cfrac{14}{3}]()