find the curvature, K, of the plane curve at the given point:?

Question

r(t) = -2t i + (7/t) j , t=1

Answer 1

r'(t) = -2i -7j/t^2
r"(t) = -14j/t^3
So K = |-14j/t^3)|/(1+ (-2i-7j)^2)^1.5