deffunc H₁( Element of NAT ) -> Element of the carrier of X = a * (S . $1);
ex S being sequence of X st
for n being Element of NAT holds S . n = H₁(n) from FUNCT_2:sch 4();
hence ex b₁ being sequence of X st
for n being Element of NAT holds b₁ . n = a * (S . n) ; :: thesis: verum