Find the least positive value of k for which the equation has real roots.
For a quadratic equation, ax2 + bx + c = 0,
D = b2 – 4ac
If D ≥ 0, roots are real
⇒ D = k2 – 16
Thus, k2 – 16 ≥ 0
⇒ k ≥ 4 or k ≤-4
Thus, least positive value of k is 4.