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My calculus book is confusing and I am pretty sure this is an error. It describes a function as one where one distinct input will have one and only one distinct output. Fair enough.

The next example is output of f(x) = square root (x) when input is 25!

Clearly, this is not a function! This relation (obviously) does not result in a unique output for every unique input, right? square root (25) = +5 and -5.

Or am I missing something in function defs. The book does not even consider the negative value of a square root operation.

That's what I get for buying the idiot's guide...

Please let me know if I am missing something here.

Thanks,

Luca