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pop000
Jan 9, 2011, 03:53 AM
be f(x)=ln^2x-4^4x Defined for any Positive x.
how many of the sentences are correct?

1)the sum of the sqrt Equation f(x)=0 is e+1
2) the Derivative are become zero in the point: x=1/sqrt"e"
3) limf(x)=Infinity when x-->0+
4)f'(-1)=0

about 3 I think is not correct. But I need your help.
thanks.

galactus
Jan 9, 2011, 04:32 AM
be f(x)=ln^{2}(x)-4^{4x} Defined for any Positive x.
how many of the sentences are correct?

Do you mean the function above?


1)the sum of the sqrt Equation f(x)=0 is e+1

sum of sqrt equation?


2) the Derivative are become zero in the point: x=\frac{1}{\sqrt{e}}

Assuming the f(x) I have above is correct, f'(x)=\frac{2ln(x)}{2}-8ln(2)\cdot 4^{4x}. Plug in x=\frac{1}{\sqrt{e}} and see if you get 0 as a result.


3) \lim_{x\to 0^{+}}f(x)=\infty

This is obviously true. You can see it from the graph as well.


4)f'(-1)=0

If you plug x=-1 into f(x), do you get 0?


about 3 i think is not correct.

Assuming I interpreted f(x) correctly, you apear to be correct.

Which one IS correct?



thanks.

pop000
Jan 9, 2011, 09:35 AM
no the function I mean is almost like you showed the part one as you showed with ln^2(x) is correct but the Part Two is not correct is need to be ln^4(x).

thank you.

pop000
Jan 9, 2011, 09:36 AM
no the function I mean is almost like you showed the part one as you showed with ln^2(x) is correct but the Part Two is not correct is need to be ln^4(x).

thank you.

galactus
Jan 10, 2011, 06:57 AM
Then why did you write 4 instead of ln? You have not fixed the typo.

pop000
Jan 10, 2011, 08:07 AM
Yes sorry is was my mistake.

galactus
Jan 10, 2011, 08:18 AM
That's OK. It will not allow you to edit now. That should be changed in the event of cases like this.