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### #102516Help! Posted by on 28 September 2009 - 03:08 PM in Problem Questions

heyyy okies for example just say you have -

f(x) = x +6 and g(x)= 3x

and you are asked to find f(g(x))

you take the g first as thats the letter in the bracket so you would have -
f(g(x)) = f(3x)

and then you deal with teh f function so you now teat the g function as the x so you have -

f(3x)= 3x +6

g(x+6)= 3(x + 6)

hope ive helped xxx Posted by on 28 September 2009 - 02:57 PM in Problem Questions

heyy everyone im really struggling to come to terms with optimsation, ive got to answer this question but i really have no idea how to do it can u please have a look at it and see if u can show me how i go about doing it, thanks so much!

... A childs drinking beaker is in the shape of a cylinder with a hemisperical lid and a circular flat base. the radius of the cylinder is r cm and the height is h cm. the volume of the cylinder is 400cm cubed.

show that the surface area of plastic, A®, needed to make the beaker is given by A®= 3pi squared + 800/r .

( the curved surface area of a hemispere of radius is 2pi squared)

i also have to find the value of r which ensures that the surface area of plastic is minimised =S

thank you again xx 