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# C3 functions watch

1. Guys are the first two lines of the solution a rule or is it just for this case??? We're finding the points where the two functions meet
2. (Original post by pondsteps)

Guys are the first two lines of the solution a rule or is it just for this case??? We're finding the points where the two functions meet
Just for this case. You really need to show the whole question as typically part (c) will be related to earlier parts.
3. (Original post by Mr M)
Just for this case. You really need to show the whole question as typically part (c) will be related to earlier parts.
Oh sorry I just attached it... Why in this case did it use this method? What made it possible to do f(x) = x
Attached Images

4. (Original post by Mr M)
Just for this case. You really need to show the whole question as typically part (c) will be related to earlier parts.
The inverse function of x is also obtained by reflecting f(x) in the line y=x, so the second line I think is true for all cases since the two will meet along the line y=x and so f(x)=x
5. (Original post by pondsteps)

Guys are the first two lines of the solution a rule or is it just for this case??? We're finding the points where the two functions meet
It's a rule. If a function and its inverse intersect, the point will always be on y=x (try drawing a function that doesn't) , so you save time by equating the function to x and solving rather than equating to the inverse function and solving.
6. Thanks so much!
7. Also when we move the function to the other side of the equation it gives the inverse of the function right?????
8. (Original post by pondsteps)
Also when we move the function to the other side of the equation it gives the inverse of the function right?????
What you've said doesn't make much sense.

An inverse function of a one-to-one mapping is a reflection in the line geometrically. So when you have then you must firstly substitute x's for y's and y's for x's (in other words, x and y variables swap places) and then you must rearrange for new

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