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How do you find the domain of a function algebraically?
Can I find the domain of a function with a calculator?
I've been looking at all sorts of tutorials and walkthroughs on youtube and math-online, but I really can't get it
Please explain to me like I'm the idiot I am :)
You're quite right; the book is using the term "domain" incorrectly. What they mean is "the greatest possible subset of the real numbers that could be used as the domain of a function whose values are given by this formula".
As you say, the domain of a function is part of its definition. The "definitions" of $f$ and $g$, in the context of the question, are not definitions at all, but merely equations. I would reformulate the question as: what is the largest domain in $\mathbb{R}$ for which this equation defines a function?
I've watched several videos, but they seemed to be doing different ways to write it. For example some domain would be; D [ 0, ∞] and some will be; Domain: { xER | x ≠ 0} Can anyone explain what's the difference between the two?