# Homework Help: Which of the following has y=-1 as an asymptote?

1. Jul 2, 2008

### pooka

Which of the following has y=-1 as an asymptote?
1.e^(-x)
2.sin(x)
3.ln x
4.x/(x+1)
5.(3-2x^2)/(2x^2-13x+7)

I've graphed each one on my calculator and I think that 1 is the answer, but it seems that it has y=0 as its asymptote rather than y=-1.

2. Jul 2, 2008

### rocomath

Re: asymptote

3. Jul 3, 2008

### chukie

Re: asymptote

I only used my calculator, but I thought about it for #4, asymptote should be x=-1 and for sin(x) there is definitely an x value for y=-1.

4. Jul 3, 2008

### rocomath

Re: asymptote

Are you on a 2nd username?

5. Jul 3, 2008

### chukie

Re: asymptote

Sorry, I went on my brother's account by mistake.

6. Jul 3, 2008

### rocomath

Re: asymptote

It's okay, it was just funny to read your post as if you were pooka.

Anyways, yes sinx has the value y=-1 but would that be considered an asymptote? It bounces between $$|\sin x|\leq 1$$

How about #5? What have you learned about the powers in the numerator and denominator that relate to the asmyptote?

7. Jul 3, 2008

### chukie

Re: asymptote

Oh so the answer should be #5. I remember if you took the limit of that it would be -1, which means the horizontal asymptote is y=-1.

8. Jul 3, 2008

### rocomath

Re: asymptote

Yep.

$$\lim_{x\rightarrow\pm\infty}\frac{3-2x^2}{2x^2-3x+7}$$

9. Jul 3, 2008

### chukie

Re: asymptote

Thanks!