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# C3 functions watch

1. Does anyone have a foolproof method for working out range and domain of any function? Even though theyre only 1 or 2 marks, they are the hardest questions in C3 and Im aiming for an A*
2. (Original post by Nayzar)
Does anyone have a foolproof method for working out range and domain of any function? Even though theyre only 1 or 2 marks, they are the hardest questions in C3 and Im aiming for an A*
For domain, think of any values that make the function not work... no real easy/quick way of doing this, but all you need to know is what usually breaks a function simpler than the one you have, and how that relates to what you have. (Eg if you're asked to find the domain of ln(2x+5), you know that the 'simpler' function lnx has a domain of x>0, so you know that 2x+5 needs to be >0.

For the range.. put in large values of x like 100000 and -100000 if it makes sense to and see what happens. Skech the graph if possible and try to find the range that way.
3. (Original post by Nayzar)
Does anyone have a foolproof method for working out range and domain of any function? Even though theyre only 1 or 2 marks, they are the hardest questions in C3 and Im aiming for an A*
I've written two, very detailed, posts over the past year or so that explains domains and ranges - if you could just take a few minutes to sit down and read them, it'll be worth your while (hopefully).

Post 1 and Post 2.
4. Fanks goyz

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