b
= b
{scope}
Put $t=1/z$ and $y(t)=w(1/t)$. Since
$$
w'=-t^2y',
\qquad
w''=t^4y''+2t^3y',
$$
the transformed equation is
$$
y''+\left(\frac2t-\frac{p(1/t)}{t^2}\right)y'
+\frac{q(1/t)}{t^4}y=0.
$$
= b
{scope}
Put $t=1/z$ and $y(t)=w(1/t)$. Since
$$
w'=-t^2y',
\qquad
w''=t^4y''+2t^3y',
$$
the transformed equation is
$$
y''+\left(\frac2t-\frac{p(1/t)}{t^2}\right)y'
+\frac{q(1/t)}{t^4}y=0.
$$