let b, a be Real; :: thesis: for Z being open Subset of REAL
for f being PartFunc of REAL ,REAL st Z c= dom ((- (2 / (3 * b))) (#) ((#R (3 / 2)) * f)) & ( for x being Real st x in Z holds
( f . x = a - (b * x) & b <> 0 & f . x > 0 ) ) holds
( (- (2 / (3 * b))) (#) ((#R (3 / 2)) * f) is_differentiable_on Z & ( for x being Real st x in Z holds
(((- (2 / (3 * b))) (#) ((#R (3 / 2)) * f)) `| Z) . x = (a - (b * x)) #R (1 / 2) ) )
let Z be open Subset of REAL ; :: thesis: for f being PartFunc of REAL ,REAL st Z c= dom ((- (2 / (3 * b))) (#) ((#R (3 / 2)) * f)) & ( for x being Real st x in Z holds
( f . x = a - (b * x) & b <> 0 & f . x > 0 ) ) holds
( (- (2 / (3 * b))) (#) ((#R (3 / 2)) * f) is_differentiable_on Z & ( for x being Real st x in Z holds
(((- (2 / (3 * b))) (#) ((#R (3 / 2)) * f)) `| Z) . x = (a - (b * x)) #R (1 / 2) ) )
let f be PartFunc of REAL ,REAL ; :: thesis: ( Z c= dom ((- (2 / (3 * b))) (#) ((#R (3 / 2)) * f)) & ( for x being Real st x in Z holds
( f . x = a - (b * x) & b <> 0 & f . x > 0 ) ) implies ( (- (2 / (3 * b))) (#) ((#R (3 / 2)) * f) is_differentiable_on Z & ( for x being Real st x in Z holds
(((- (2 / (3 * b))) (#) ((#R (3 / 2)) * f)) `| Z) . x = (a - (b * x)) #R (1 / 2) ) ) )
assume A1: ( Z c= dom ((- (2 / (3 * b))) (#) ((#R (3 / 2)) * f)) & ( for x being Real st x in Z holds
( f . x = a - (b * x) & b <> 0 & f . x > 0 ) ) ) ; :: thesis: ( (- (2 / (3 * b))) (#) ((#R (3 / 2)) * f) is_differentiable_on Z & ( for x being Real st x in Z holds
(((- (2 / (3 * b))) (#) ((#R (3 / 2)) * f)) `| Z) . x = (a - (b * x)) #R (1 / 2) ) )
then A2: Z c= dom ((#R (3 / 2)) * f) by VALUED_1:def 5;
then for y being set st y in Z holds
y in dom f by FUNCT_1:21;
then A3: Z c= dom f by TARSKI:def 3;
A4: for x being Real st x in Z holds
f . x = ((- b) * x) + a

proof

let x be Real; :: thesis: ( x in Z implies f . x = ((- b) * x) + a )
assume x in Z ; :: thesis: f . x = ((- b) * x) + a
then f . x = a - (b * x) by A1;
hence f . x = ((- b) * x) + a ; :: thesis: verum

end;

then A5: ( f is_differentiable_on Z & ( for x being Real st x in Z holds
(f `| Z) . x = - b ) ) by A3, FDIFF_1:31;

now

let x be Real; :: thesis: ( x in Z implies (#R (3 / 2)) * f is_differentiable_in x )
assume A6: x in Z ; :: thesis: (#R (3 / 2)) * f is_differentiable_in x
then A7: f is_differentiable_in x by A5, FDIFF_1:16;
f . x > 0 by A1, A6;
hence (#R (3 / 2)) * f is_differentiable_in x by A7, TAYLOR_1:22; :: thesis: verum

end;

then A8: (#R (3 / 2)) * f is_differentiable_on Z by A2, FDIFF_1:16;
for x being Real st x in Z holds
(((- (2 / (3 * b))) (#) ((#R (3 / 2)) * f)) `| Z) . x = (a - (b * x)) #R (1 / 2)

proof

let x be Real; :: thesis: ( x in Z implies (((- (2 / (3 * b))) (#) ((#R (3 / 2)) * f)) `| Z) . x = (a - (b * x)) #R (1 / 2) )
assume A9: x in Z ; :: thesis: (((- (2 / (3 * b))) (#) ((#R (3 / 2)) * f)) `| Z) . x = (a - (b * x)) #R (1 / 2)
then A10: f is_differentiable_in x by A5, FDIFF_1:16;
A11: 3 * b <> 0 by A1, A9;
A12: ( f . x = a - (b * x) & f . x > 0 ) by A1, A9;
(((- (2 / (3 * b))) (#) ((#R (3 / 2)) * f)) `| Z) . x = (- (2 / (3 * b))) * (diff ((#R (3 / 2)) * f),x) by A1, A8, A9, FDIFF_1:28
.= (- (2 / (3 * b))) * (((3 / 2) * ((f . x) #R ((3 / 2) - 1))) * (diff f,x)) by A10, A12, TAYLOR_1:22
.= (- (2 / (3 * b))) * (((3 / 2) * ((f . x) #R ((3 / 2) - 1))) * ((f `| Z) . x)) by A5, A9, FDIFF_1:def 8
.= (- (2 / (3 * b))) * (((3 / 2) * ((a - (b * x)) #R ((3 / 2) - 1))) * (- b)) by A3, A4, A9, A12, FDIFF_1:31
.= ((2 / (3 * b)) * ((3 * b) / 2)) * ((a - (b * x)) #R ((3 / 2) - 1))
.= 1 * ((a - (b * x)) #R ((3 / 2) - 1)) by A11, XCMPLX_1:113
.= (a - (b * x)) #R (1 / 2) ;
hence (((- (2 / (3 * b))) (#) ((#R (3 / 2)) * f)) `| Z) . x = (a - (b * x)) #R (1 / 2) ; :: thesis: verum

end;

hence ( (- (2 / (3 * b))) (#) ((#R (3 / 2)) * f) is_differentiable_on Z & ( for x being Real st x in Z holds
(((- (2 / (3 * b))) (#) ((#R (3 / 2)) * f)) `| Z) . x = (a - (b * x)) #R (1 / 2) ) ) by A1, A8, FDIFF_1:28; :: thesis: verum