# Asymptotes math problem

1. Jun 6, 2010

### rshalloo

1. The problem statement, all variables and given/known data

f(x) = 1/(x+1)

If tangents to curve at x=x1 and x=x2 are parrallel and if x1 is not equal to x2
show that x1 + x2 = -2

3. The attempt at a solution

Well i found my equations for the asymptotes
Horizontal: x=0
Vertical: x= -1

and then i would say that if they were parrallel that the slopes are equal and therefore at the point x1 and the point x2 the slopes are equal

f1(x) = -1/(x+1)2

If i sub in x1 and x2, they will be equal and the question says they arent?

1. The problem statement, all variables and given/known data

2. Relevant equations

3. The attempt at a solution

2. Jun 6, 2010

### Staff: Mentor

Re: Asymptotes

Your title is misleading - this problem doesn't have anything to do with asymptotes of either kind.

You are give that the tangent lines are parallel at x = x1 and x = x2, so f'(x1) = f'(x2). This means that -1/(x1 + 1)2 = -1/(x2 + 1)2. Solve that equation, keeping in mind that x1 $\neq$ x2, and that if a2 = b2 ==> a = b or a = -b.

3. Jun 6, 2010

### rshalloo

Re: Asymptotes