sian duuno problems with maxima and minima sure fail this time..
Originally posted by ZaiDancerz:sian duuno problems with maxima and minima sure fail this time..
Well, the forummers did try to help you out, but it didn't work.
Why not you call up your friends NOW, and ask them for help instead?
Originally posted by ZaiDancerz:sian duuno problems with maxima and minima sure fail this time..
how did you fare in your previous a.math tests?( topics on differentiation, surds, etc.)
during the test, copy from your friends
Dear ZaiDancerz,
Try to write something in your test.
Typically, a problem on maxima and minima will ask you to show a result (e.g. area, volume, cost, etc. Then you will proceed to find its maximum or minimum.
Nevermind if you can't show the result. Just carry out differentiation on the result and find the stationary value(s). Then carry out differentiation again to determine the nature. You will score some marks by doing these.
Example:
(a) Show that the volume V of the cuboid is given by V = 360 x^2 - 6 x^3.
(b) Find the value of x for which V is stationary.
(c) Determine the nature of the stationary point and hence find its value.
You can proceed to answer (b) and (c), skipping (a) if you are stuck.
For (b), we first differentiate V with respect to x, i.e.,
dV / dx = 720 x - 18 x^2.
For stationary V, equate dV / dx to zero and solve for x, i.e.,
720 x - 18 x^2 = 0
18 x (40 - x) = 0
x = 40.
For (c), we first differentiate dV / dx with respect to x, i.e.,
d^2 V / dx^2 = 720 - 36 x.
When x = 40, d^2 V / dx^2 = 720 - 36(40) < 0, so x = 40 gives maximum V.
When x = 40, maximum V = 360 (40^2) - 6 (40^3) = 192 000.
Good luck!
Cheers,
Wen Shih
Originally posted by ZaiDancerz:sian duuno problems with maxima and minima sure fail this time..
Mr Wee has suggested some ways whereby you can get some marks during the test.
However, you should learn from the first concept after the test and progress from one concept to another and from one example to another until you have understood the whole topic.
You should stay back in school everyday to seek help from your Add Maths School Teacher.