Calculus: I keep getting this question wrong can you help?

Ok here is the question:

Find the equation of the tangent line to the graph of -2x/(x^2+1) at the Origin and at the point (1,-1)

I got 4 of these right in a row but keep getting wrong answers for this one. please show the steps used along with the answer so I know where I went wrong

?2010-09-26T12:07:32Z

Favorite Answer

y = -2x/(x²+1)
y' = [-2(x²+1) + 2x(2x)]/(x²+1)² = (4x²-2x²-2)/(x²+1)² = 2(x²-1)/(x²+1)²

y'(0) = -2
y'(1) = 0

The tangent line at the origin has slope -2 and passes through point (x,y) = (0,0):
y = -2x
The tangent line at the point (1,-1) has slope 0 (horizontal) and passes through the point (x,y) = (1,-1):
y = -1
...