3U 1999 Q5b) (1 Viewer)

[mreditor16]

So, here it is:



I'm concerned about part ii). I'm looking for the advice of people such as Carret, Trebla, RN, Braintic and Drongoski in particular.

What would be a satisfactory method for it? Because saying (0,0) is a minimum and the only stat pt as your reasoning is apparently not enough, as suggested by the Notes from the Marking Centre published by BOSTES:




So how do you answer this 3U Q? :O

 

[mreditor16]

anyone??

 

[QZP]

f(0) = 0
Thus, f(x) >=0 for all x since minimum at x = 0 from (i)

What would be a satisfactory method for it? Because saying (0,0) is a minimum and the only stat pt as your reasoning is apparently not enough, as suggested by the Notes from the Marking Centre published by BOSTES:

This is fine because you evaluated f(0). Marking critera says its unsatisfactory if you didn't (because minimum could be -1 or something)

 

[mreditor16]

f(0) = 0
Thus, f(x) >=0 for all x since minimum at x = 0 from (i)



This is fine because you evaluated f(0). Marking critera says its unsatisfactory if you didn't (because minimum could be -1 or something)

anyone willing to confirm??

 

[Carrotsticks]

anyone willing to confirm??

I can confirm that he is correct.

Saying that there is a minimum point St x=-1 is insufficient because it could be that the minimum point is at (0,-3) for example. It is needed to demonstrate that this minimum point is equal to, or greater than zero.

 

[mreditor16]

okay thanks guys!

 

[RealiseNothing]

hahahaha lost it at "the markers were perplexed by the number of candidates who treated it as a quadratic"