If a, b be the roots x2+px−q=0 and g,d be the roots of x2+px+r=0 , q+r =1 then (a−g)(a−d)(b−g)(b−d) is ……
1
Here, a+b= -p
g+d = -p
then a+b= g+d
now, (a-g)(a-d)= a2– a(g+d)+gd
=a2–a(a+b)+r = -ab +r = -(-q)+r = q+r
By symmetry of the results (b-g)(b-d)= q+r
Hence , the ratio is 1