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- bobbym
- 2011-09-30 02:16:23
Hi Deon588;
Your welcome. What year are you in?
- Deon588
- 2011-09-30 02:13:34
Thanks a lot Bob and Bobbym. I have done this many times before but the way the question was written confused me a bit
- bob bundy
- 2011-09-30 01:59:46
hi Deon588
will do nicely.
(But using the 'a' and 'b' from the new quadratic, of course.)
Bob
- bobbym
- 2011-09-30 01:14:31
Hi Deon588;
Yes, there is a way using just algebra.
- Deon588
- 2011-09-29 20:02:29
Hi Bob. Differential calculus is not part of my course this year at all. So I can find x either by completing the square or
?If i'm asking for help too much lately please let me know. I have exams in 3 weeks so trying to get everything cleared up before the exam.
Thanks
- bob bundy
- 2011-09-29 17:51:32
hi Deon588
d(BA)/dx is a special notation used in the differential calculus.
It gives you a way of finding the maximum value of an expression (amongst many, many uses!).
It's too big a topic to start in answer to the question, if you haven't met it before.
But don't worry. As the expression
is a quadratic there's another way to get the maximum value.
I've put the graph below. As you can see it does have a maximum value. Would you be able to work out the x, at this point?
Bob
- Deon588
- 2011-09-29 17:33:41
Hi Bob. I did exactly that up to the point
Thanks
- bob bundy
- 2011-09-29 11:03:09
hi Deon588
I got a = -2 b = -4 and c = 0
Then for the points:
So
So you need
Can you take over from here?
Bob
- Deon588
- 2011-09-29 09:00:09
Hi Bob I have the parabola and lines equations. So to find the maximum I subtracted the line's equation from the parabola's equation but from here i'm not sure.
- bob bundy
- 2011-09-29 07:56:48
hi Deon588,
Have you got a, b and c yet?
I'll assume yes.
That fixes the parabola (ie. there's only one answer) and the line is obviously unique.
But B can move about on the parabola and so that means M moves too.
I'd call M (x,0) and write the coordinates of B and A in terms of this.
Then you write an expression for BA in terms of x, differentiate, and hence get the maximum.
I'd better go and get a piece of paper and try it out.
Bob
- Deon588
- 2011-09-29 07:31:35
Hi. I am a bit confused with this question the question is "Find the coordinates of M when BA is a maximum" Should I subtract the straight line from the parabola and then
I don't understand how BA has any effect on M? Doesn't M just stay where it is on the x-axis?Thanks a lot in advance