Hi

Some questions I can't do. This one is Q6. The textbook answers are

x < - 2^0.5,x > 2^0.5

BTW I MEAN +/- ROOT 2 FOR THE LAST BIT OF WORKING

Printable View

- Oct 23rd 2007, 02:38 PMApexGeneral differentiation questions
Hi

Some questions I can't do. This one is Q6. The textbook answers are

**x < - 2^0.5**,**x > 2^0.5**

BTW I MEAN +/- ROOT 2 FOR THE LAST BIT OF WORKING

- Oct 23rd 2007, 02:47 PMJhevon
hint. a fraction is negative (that is less than zero) if we divide a negative number by a positive number, and vice versa (obviously, division by 0 is a no-no).

the denominator of f'(x) is a perfect square, thus it is always greater than or equal to zero. so to find where f'(x) < 0, we simply solve for where the numerator is < 0

so you want to solve

you ended up doing this, but your mistake was this: if then - Oct 23rd 2007, 03:07 PMApex
Hi

Is -2^0.5 equivalent to (-2)^0.5 :. wrong?

I don't see how to get to the final answer though. How do I know which way round the inequalities are, and whether the solutions are seperate from eachother?

Question 7 is below.

The textbook answer is x<4

Thanks v much

Apex - Oct 23rd 2007, 03:13 PMJhevon
yes, that is wrong.

while ...which is not a real number

Quote:

I don't see how to get to the final answer though. How do I know which way round the inequalities are, and whether the solutions are seperate from eachother?

- Oct 23rd 2007, 03:15 PMJhevon
- Oct 23rd 2007, 03:27 PMApex
Oh yeh thanks. I did it wrong way round. As for the numberline idea, I think there is a graphical method of doing this (how do my graphs help)? I need the graphical way if it's possible.

I've also tried Q8, which I get incorrect answers for.

Textbook answers are 0.25, 1.57, 2.89, 4.71.

Thanks so much! - Oct 23rd 2007, 03:39 PMApex
Hello,

This is question 9. Textbook doesn't say anything about it (it usually leaves "prove" answers out).

I'll post more questions tomorrow, unless I can somehow manage to complete them all correctly :P

Thanks :) - Oct 23rd 2007, 04:59 PMJhevon
- Oct 23rd 2007, 05:02 PMJhevon
- Oct 23rd 2007, 05:06 PMJhevon
- Oct 24th 2007, 03:50 PMApex
Hi

I carried with Q9 but got stuck. See Q9 below.

Thanks alot

Apex - Oct 24th 2007, 03:53 PMApex
This one requires more of an explanation

- Oct 24th 2007, 03:53 PMApex
Stuck on solving this....

- Oct 24th 2007, 03:54 PMApex
I don't understand what this means.

- Nov 3rd 2007, 10:48 AMApex
bump