let X, Y be RealNormSpace; :: thesis: for T being LinearOperator of X,Y
for B0 being Subset of X
for a being Real holds T .: (a * B0) = a * (T .: B0)

let T be LinearOperator of X,Y; :: thesis: for B0 being Subset of X
for a being Real holds T .: (a * B0) = a * (T .: B0)

let B0 be Subset of X; :: thesis: for a being Real holds T .: (a * B0) = a * (T .: B0)
let a be Real; :: thesis: T .: (a * B0) = a * (T .: B0)
thus T .: (a * B0) c= a * (T .: B0) :: according to XBOOLE_0:def 10 :: thesis: a * (T .: B0) c= T .: (a * B0)
proof
let t be object ; :: according to TARSKI:def 3 :: thesis: ( not t in T .: (a * B0) or t in a * (T .: B0) )
assume t in T .: (a * B0) ; :: thesis: t in a * (T .: B0)
then consider z1 being object such that
z1 in the carrier of X and
A1: z1 in a * B0 and
A2: t = T . z1 by FUNCT_2:64;
consider x1 being Element of X such that
A3: z1 = a * x1 and
A4: x1 in B0 by A1;
A5: T . x1 in T .: B0 by ;
t = a * (T . x1) by ;
hence t in a * (T .: B0) by A5; :: thesis: verum
end;
let t be object ; :: according to TARSKI:def 3 :: thesis: ( not t in a * (T .: B0) or t in T .: (a * B0) )
assume t in a * (T .: B0) ; :: thesis: t in T .: (a * B0)
then consider tz0 being Point of Y such that
A6: t = a * tz0 and
A7: tz0 in T .: B0 ;
consider z0 being Element of X such that
A8: z0 in B0 and
A9: tz0 = T . z0 by ;
reconsider z0 = z0 as Point of X ;
set z1 = a * z0;
A10: a * z0 in a * B0 by A8;
t = T . (a * z0) by ;
hence t in T .: (a * B0) by ; :: thesis: verum