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wjec c3 help

does anyone know how to find the domain and range of a function? I can only do it for a quadratic
, how do you do it for a ln (x) or e^x graph?
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Avatar for B_9710
B_9710
18
Original post by trianglelifx
does anyone know how to find the domain and range of a function? I can only do it for a quadratic
, how do you do it for a ln (x) or e^x graph?

Think about the shape of the curve. These are standard functions which at C3 you are expected to just remember (as with the trig, inverse trig and minor trig functions).
For other curves it can be quite difficult to find the domain and range and sketch the curve. But the ones at C3 are just standard curves and simple transformations of these curves.
Reply 2
Avatar for nerak99
nerak99
13
The Domain being the set of possible values of x in (f(x)) and the Range being the set of possible values of f(x).

Could you post a question to which you cannot find an answer that you understand?
Original post by nerak99
The Domain being the set of possible values of x in (f(x)) and the Range being the set of possible values of f(x).

Could you post a question to which you cannot find an answer that you understand?



thanks I know but I still cant seem to find the answer
I cant do this question is Wjec c3 may 2008 9a the function f has domain x is less than or equal to -1
f(x) = (x + 1)^2 -2

find the range of f
Original post by B_9710
Think about the shape of the curve. These are standard functions which at C3 you are expected to just remember (as with the trig, inverse trig and minor trig functions).
For other curves it can be quite difficult to find the domain and range and sketch the curve. But the ones at C3 are just standard curves and simple transformations of these curves.


ok thanks but I don't know how transform lnx or e^x graphs
Original post by trianglelifx
thanks I know but I still cant seem to find the answer
I cant do this question is Wjec c3 may 2008 9a the function f has domain x is less than or equal to -1
f(x) = (x + 1)^2 -2

find the range of f


You can find the minimum point from f(X), draw the graph and shade any side out of your domain you should see your range.
Reply 6
Avatar for B_9710
B_9710
18
Original post by trianglelifx
ok thanks but I don't know how transform lnx or e^x graphs


Exactly the same way as any other graph. Don't be put off by the fancy log or exponentials.
If f(x)=ex f(x)=e^x we can translate this by a a units to the right which is given by f(x−a)=ex−a f(x-a) = e^{x-a} . Exactly the same.
If g(x)=ln⁡x g(x)=\ln x and we stretch parallel to the x axis by scale factor k k this is g(x/k)=ln⁡(x/k) g(x/k)=\ln(x/k) . The transformations are exactly the same as any other function, whether it be a quadratic, cubic, exponential etc.
(edited 7 years ago)
Thanks!
Reply 8
Avatar for Zacken
Zacken
22
Original post by trianglelifx
Thanks!


If you're interested, I've written a bit about domain and ranges in the following two posts over the past year or so. :smile: Post 1 and Post 2.

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