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# C3 Functions help please :) watch

1. Just done a past paper like and it gave me f(x) = ROOT of (x + 1)
I worked out that f^-1(x) = x^2 -1

and have plotted teh graph of f^-1(x) as they asked, however the question also asks me to plot the original f(x) graph on the same grid...

will i actually have to know what f(x) looks like!? as it seems complicated? or is there some sort of "flip or transformation" relating f(x) and f^-1(x) graphs

Thanks alot Xd
2. Yes - reflect in the line y=x
3. The graph of f^-1(x) is the graph of f(x) reflected in the line y=x.

Once you've done this, if (as you wrote) f(x) is the positive root of x+1 then you should delete any part of the curve which lies below the x axis since the square root of a number is never negative.

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