Find the function whose graph is stretched horizontally

Question

Find the function whose graph is stretched horizontally.(k > 1)
f(1kx)
1kf(x)
kf(x)
f(kx)

Answer 1

f(1kx) is the answer. The 1 in front of the k, in the 'argument,' is UNNECESSARY and wouldn't be present, conventionally. So the real answer should be just f(kx).