Which of the following sets are convex?
(a) {(x, y) : x2 + y2≥ 1}
(b) {(x, y) : y2 ≥ x}
(c) {(x, y) : 3x2 + 4y2 ≥ 5}
(d) {(x, y) : y ≥ 2, y ≤ 4}
Open in App
Solution
(d) {(x, y) : y ≥ 2, y ≤ 4}
{(x, y) : y ≥ 2, y ≤ 4} is the region between two parallel lines, so any line segment joining any two points in it lies in it. Hence, it is a convex set.