One D/S question

lololo

What is the value of k^2-k? 1). The value of k-1/k is 1, 2). The value of 2k-1 is 5^1/2

Can anybody expain why the answer is D instead of B? Thank you very much.

liuliyun

k-1/k=1

k*k-1=k

k*k-k=1