let f be PartFunc of REAL,REAL; :: thesis:
let a, b be Real; :: thesis:
assume that
A1: [.a,b.[ c= dom f and
A2: f is_right_ext_Riemann_integrable_on a,b ; :: thesis:
for r being Real holds
( r (#) f is_right_ext_Riemann_integrable_on a,b & ext_right_integral ((r (#) f),a,b) = r * (ext_right_integral (f,a,b)) )

proof

let r be Real; :: thesis:
consider Intf being PartFunc of REAL,REAL such that
A3: dom Intf = [.a,b.[ and
A4: for x being Real st x in dom Intf holds
Intf . x = integral (f,a,x) and
A5: Intf is_left_convergent_in b and
A6: ext_right_integral (f,a,b) = lim_left (Intf,b) by A2, INTEGR10:def 3;
set Intfg = r (#) Intf;
A7: r (#) Intf is_left_convergent_in b by A5, LIMFUNC2:43;
A8: ( dom (r (#) Intf) = [.a,b.[ & ( for x being Real st x in dom (r (#) Intf) holds
(r (#) Intf) . x = integral ((r (#) f),a,x) ) )

proof

thus A9: dom (r (#) Intf) = [.a,b.[ by A3, VALUED_1:def 5; :: thesis:
let x be Real; :: thesis:
assume A10: x in dom (r (#) Intf) ; :: thesis:
then A11: a <= x by A9, XXREAL_1:3;
then A12: ['a,x'] = [.a,x.] by INTEGRA5:def 3;
A13: x < b by A9, A10, XXREAL_1:3;
then A14: [.a,x.] c= [.a,b.[ by XXREAL_1:43;
A15: ( f is_integrable_on ['a,x'] & f | ['a,x'] is bounded ) by A2, A11, A13, INTEGR10:def 1;
thus (r (#) Intf) . x = r * (Intf . x) by A10, VALUED_1:def 5
.= r * (integral (f,a,x)) by A3, A4, A9, A10
.= integral ((r (#) f),a,x) by A1, A11, A12, A14, A15, INTEGRA6:10, XBOOLE_1:1 ; :: thesis:

end;

for d being Real st a <= d & d < b holds
( r (#) f is_integrable_on ['a,d'] & (r (#) f) | ['a,d'] is bounded )

proof

let d be Real; :: thesis:
assume A16: ( a <= d & d < b ) ; :: thesis:
then A17: ( ['a,d'] = [.a,d.] & [.a,d.] c= [.a,b.[ ) by INTEGRA5:def 3, XXREAL_1:43;
A18: ( f is_integrable_on ['a,d'] & f | ['a,d'] is bounded ) by A2, A16, INTEGR10:def 1;
['a,d'] c= dom f by A1, A17;
hence ( r (#) f is_integrable_on ['a,d'] & (r (#) f) | ['a,d'] is bounded ) by A18, INTEGRA6:9, RFUNCT_1:80; :: thesis:

end;

hence A19: r (#) f is_right_ext_Riemann_integrable_on a,b by A8, A5, LIMFUNC2:43, INTEGR10:def 1; :: thesis:
lim_left ((r (#) Intf),b) = r * (ext_right_integral (f,a,b)) by A5, A6, LIMFUNC2:43;
hence ext_right_integral ((r (#) f),a,b) = r * (ext_right_integral (f,a,b)) by A8, A7, A19, INTEGR10:def 3; :: thesis:

end;

hence for r being Real holds
( r (#) f is_right_ext_Riemann_integrable_on a,b & ext_right_integral ((r (#) f),a,b) = r * (ext_right_integral (f,a,b)) ) ; :: thesis: