Given, parabola is y2=4x+16 y2=4(x+4) Let parametric point on parabola be (t2−4,2t) distance OP≤k (t2−4)2+4t2≤k2 t4+16−8t2+4t2≤k2 t4−4t2+16−k2≤0 D≤0 ⇒‌‌16−4(16−k2)≤0 ⇒‌‌4−16+k2≤0⇒k2≤12 k∈[−2√3,2√3]