find the domain of the logarithmic function:
f(x)=ln(x^2+3x-4)

Question

find the domain of the logarithmic function:
f(x)=ln(x^2+3x-4)

anonymous · Answer

basically, whats inside the parentheses cannot be equal to or less than zero

anonymous · Answer

or put an equivalent way, solve $x^2+3x-4>0$

anonymous · Answer

so i factor the problem, and get -4 and 1, so is that the domain? or can it not be negative...

anonymous · Answer

$x^2+3x-4$ is a parabola that opens up. you found the zeros via $(x+4)(x-1)=0$ so your parabola will be negative between the zeros and positive outside them

anonymous · Answer

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anonymous · Answer

you have to make sure it is positive, so your answer should look like 
$x<-1$ or $x>4$ 
or perhaps $(-\infty, -1)\cup (4,\infty)$

anonymous · Answer

thanks! that's exactly what i was looking for

anonymous · Answer

Just a little typo: x < -4 or x > 1

anonymous · Answer

i'll say it was a typo.
comletey wrong in fact.
cholorphll has the right answer

anonymous · Answer

$$(-\infty, -4)\cup (1,\infty)$$

anonymous · Answer

@satellite73 I just jump in at the last minute to switch the sign!