as we know that sub duplicate is ntng but square root
p:q=square root of p-x(square/q-x(square
apply square on both sides then we get
p(square/q(square=p-x(square/q-x(square
cross multiply we get
p(square)q-x(square)p(square)=q(square)p-q(square)x(square)
then we get
x(square)=pq/p+q