6X/[X(X-1)]=(X+3)/[X(X-1)]-[K(X-1)]/[X(X-1)]
6X=X+3-K(X-1)
6X-X-3+KX-K=0
(5+K)X=K+3
X=(K+3)/(5+K)
所以K的取值范围5+K≠0
K≠-5