1) the line passing through C and D has a slope of (3-1)/(-5-1) = -3 = the slope of the line passing through A and B, therefore, (4-3)/(a-3) = -3, a=8/3 2) by solving the simultaneous equations, we can get x=-1, i.e., b=-1 3) (x+q)(x-p) = x^2+(q-p)x-pq q-p=p