Use Newton's method to approximate to within 10^-4, the value of x that produces the point on the graph of y = 1/x that is closest to (2, 1).

I tried setting p0 = 2 and using the algorithm $\displaystyle p_{n} = p_{n-1} - f(p_{n-1})/f'(p_{n-1})$ where f(x) = 1/x and f'(x) = -1/x^2 but the number is actually increasing? It goes 4, 8, 16, 32, ...

I'm not sure what I'm doing wrong here.