F4 maths 一元二次方程

For unequal real roots, delta > 0
(-4k)^2 - 4(4)k(k - 1) > 0
16k^2 - 16k(k - 1) > 0
k^2 - k^2 + k > 0
k > 0
That means k can be any value greater than zero, that is k can be any positive number.