Whats a good way to improve in minima and maxima (1 Viewer)

[Winston]

Hey guys for somereason i can never get these questions

any tips or tricks i mean the first bit , getting a equation is the hardest

 

[kini mini]

I'm not sure exactly where you are having problems - can you post a sample question so I or someone else can work you through it?

 

[asl2]

when you have a equation... y= something

* differentiate it first... dy/dx = something
* stationary points occour when dy/dx =0

so...

0=something

when you solve this equation you will get the x values (which are max and min)

you can then either use second diretivie or the substuting in value thing to find out if it is max min, or inflection

 

[tooheyz]

^ yeah as asl2 said, but if u use the second derivative if:
- y'' > 0 then it is a minimum
- y''< 0 then it is a max

but yeah the easier way to find the nature is to do the box and draw the little lines underneath them

you should give us a sample question and your working so we know exactly what your troubles are.

 

[Winston]

basically the most problems i have is

forming the equation through the wording

and then it says

show that the equation or perimteter is the following


uno that part of max and min questions

thats the hardest of all thats it

 

[Rahul]

u need to know important features of y' and y''. like when they are positive/negative, or when they r zero.

and somebody mentioned earlier to draw the table of values....that makes it a whole lot easier too.

forming the two equations is often the hard part

 

[tooheyz]

yeah normally they 'give' you 2 equations through the wording. like the perimeter, and the area. or the volume and the area.

so you might get a 100m wire is used to cover a rectangluar piece of land. so you let the sides be equal to something like 'x' and 'y' and your first equation becomes:

perimeter = x + x + y + y = 2x + 2y
but perimter = 100m
.'. 50 = x + y

then to find the area it is Area = xy

then you solve the equations simulaneously

 

[Winston]

yeah thats my main concern , getting the equation
and proving the equation is the one given

ahh i guess im not good with words lol

 

[tooheyz]

the more questions you do, the more you will get it. so i suggest you keep practising. in 2u they can only ask u those tuype of questions - perimeter/area or area/volume ... or in some cases perimeter/volume

so just get serveral questions from different sources and do em. i use to have difficulty as well, but i just kept on practicing.. and now its not so hard. its like series n sequences, the more u do it, you will c a pattern

 

[Rahul]

sometimes u have to come-up wid equations....they are not necessarily given. eg: there was one q when u had to relate the diagonal of a rectangle and an equation of a circle when it had its vertices on the circle...may not understand what i am saying....they had given a diagram, not the equation itself

 

[tooheyz]

yeah that sounds a tad hard for 2u. r u sure thats for 2u or 3u?

 

[Rahul]

it was in an old 2u book

practice is the best advise