MATLAB: Simple expression is not simplified (Symbolic Toolbox)

symbolic

Quite simple code
syms a b
assume(a,'real');
assume(b,'real');
simplify((-1)^a*(b-1)^a)
The answer is obviously (1-b)^a, but Matlab does not simplify it? Why? How to make it work?
Thank you!

Best Answer

That is not a correct solution.
Let b = -31, let a = 3/5
simplify((1-(-31))^(3/5));
                               8
simplify((-1)^(3/5)*((-31)-1)^(3/5));
                                 (1/5)
                          -8 (-1)     
evalf(%);
                  -6.472135955 - 4.702282018 I
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