deffunc H₁( Element of NAT ) -> Element of REAL = f . (b * $1);
consider h being sequence of REAL such that
A1: for n being Element of NAT holds h . n = H₁(n) from FUNCT_2:sch 4();
take h ; :: thesis: for n being Element of NAT holds h . n = f . (b * n)
let n be Element of NAT ; :: thesis: h . n = f . (b * n)
thus h . n = f . (b * n) by A1; :: thesis: verum