finding maximum and minimums

[extcar]

do you say since S.P occurs at dy/dx=0
and then u get ur answer
do u have to show that it is a max or min ?
i.e: using the derivative test, and if you do use it, do you have to show working out for the points you use

[abeybaby]

you have to verify that the point is a max/min if the question asks you to find the max/min

[extcar]

even if the question is
"find the maximum area of ___"
and u get only one answer, you still gotta show it??

[abeybaby]

mmmmm... thats a tough one.. i think you do, unless its like a parabola. if it is, then you can just say "since its a negative parabola, the stationary point is a local maximum". but otherwise, I would. cos then if its a minimum, you'd have to go have a look at the end points

[extcar]

i see, thanks!
how about  when you're finding inverse functions, and you got two solutions
do you say since domf = ____ ( therefore ranf inverse = _____), or domf inverse = ___
or would both be right
e.g: neap 2010 q3 exam 1

[abeybaby]

Yeah the first thing you said is correct