simplify_fractions may have some problems?

[liushang0322]

this maybe right:

using Symbolics, LinearAlgebra
@syms G1 G2 G3 G4 H1 H2 H3
Q = zeros(Num,5,5)
Q[1,5] = -H3
Q[2,1] =  G1
Q[2,4] = -H2
Q[3,2] =  G2
Q[3,5] =  H1
Q[4,3] =  G3
Q[5,4] =  G4

P=[1 0 0 0 0]'
G=(I(size(Q,1))-Q)\P
g = G[end]
g =  expand(g)
#= g = simplify_fractions(g) =#
op = operation(g)
g1,g2 = arguments(g)
g2 = PolyForm(g2)
g2 = simplify_fractions(g2)
g = g1//g2

but this is wrong?

@syms G1 G2 G3 G4 H1 H2 H3
Q = zeros(Num,5,5)
Q[1,5] = -H3
Q[2,1] =  G1
Q[2,4] = -H2
Q[3,2] =  G2
Q[3,5] =  H1
Q[4,3] =  G3
Q[5,4] =  G4

P=[1 0 0 0 0]'
G=(I(size(Q,1))-Q)\P
g = G[end]
g =  expand(g)
g = simplify_fractions(g)