Find b & Inverse Function of g(x) = 1-x2

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Homework Statement



Let g:[b,2] -> R where g(x) = 1-x2. If b is the smallest real value such that g has an inverse function, find b and g inverse

The Attempt at a Solution



I can find the inverse function easily, but I don't understand how I go about finding b.

According to the book, answer is b=0
 
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I would just look at the graph. Start by graphing g(x) = 1-x2 with the restriction g:[-∞,2] -> R, and then look to see how much of the right portion of the graph is needed to make g(x) one-to-one.
 
right that makes sense!

In other words you can only take the inverse of a function f, if the original function f is one-to-one.

got it.