let g be polynomially-abs-bounded Function of NAT,REAL; ex d being non empty positive-yielding XFinSequence of REAL ex N being Nat st
for x being Nat st N <= x holds
|.(g . x).| <= (polynom d) . x
consider k1 being Nat such that
A4:
|.g.| in Big_Oh (seq_n^ k1)
by defabs;
consider t1 being Element of Funcs (NAT,REAL) such that
A6:
( |.g.| = t1 & ex c1 being Real ex N1 being Element of NAT st
( c1 > 0 & ( for n being Element of NAT st n >= N1 holds
( t1 . n <= c1 * ((seq_n^ k1) . n) & t1 . n >= 0 ) ) ) )
by A4;
consider c1 being Real, N1 being Element of NAT such that
A7:
( c1 > 0 & ( for n being Element of NAT st n >= N1 holds
( t1 . n <= c1 * ((seq_n^ k1) . n) & t1 . n >= 0 ) ) )
by A6;
consider d being non empty positive-yielding XFinSequence of REAL such that
A8:
for x being Nat holds c1 * (x to_power k1) <= (polynom d) . x
by LRNG2;
reconsider N = N1 + 1 as Nat ;
take
d
; ex N being Nat st
for x being Nat st N <= x holds
|.(g . x).| <= (polynom d) . x
take
N
; for x being Nat st N <= x holds
|.(g . x).| <= (polynom d) . x
let x be Nat; ( N <= x implies |.(g . x).| <= (polynom d) . x )
assume B1:
N <= x
; |.(g . x).| <= (polynom d) . x
LXN:
x is Element of NAT
by ORDINAL1:def 12;
N1 <= N
by NAT_1:12;
then
N1 <= x
by XXREAL_0:2, B1;
then A9:
( t1 . x <= c1 * ((seq_n^ k1) . x) & t1 . x >= 0 )
by A7, LXN;
A10:
(seq_n^ k1) . x = x to_power k1
by ASYMPT_1:def 3, LXN, B1;
c1 * (x to_power k1) <= (polynom d) . x
by A8;
then
t1 . x <= (polynom d) . x
by A10, A9, XXREAL_0:2;
hence
|.(g . x).| <= (polynom d) . x
by A6, VALUED_1:18; verum