Why Do Exponential Rules Affect Equations Like -(y^2-1)^(1/2) = (1-y^2)^(1/2)?

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Jumpsmash
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I have come across in the solution to a question. -(y^2-1)^(1/2)= (1-y^2)^(1/2). However I do not know why this has to be the case, and would appreciate anyone showing me, presumably using rules of exponentials, how this could be shown to be true. Similarly if the power is not fractional but either a positive or negative integer. ie. -(ax-b)^2= (b-ax)^2 or -(ax-b)^3= -(b-ax)^3

With regard to the last two, thinking about it I have an intuitive sense that if the power is even then this will make whatever is in the bracket +ve and if if it is odd then if whatever in the bracket will still be negative. But this is not really much good, and, as I say, I'd like to know how to show these to be the case.
 
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Where did you see that? Try substituting y=0 into both and you will see that they are not equal