If $A =\{(x, y): x^2 + y^2 = 25\}$ and $B=\{(x, y): x^2+9y^2=144\}$, then $A∩B$ contains
Answer & explanation
Correct answer: option 4
Clearly, A is the set of all points on the circle $x^2 + y^2 =25$ and B is the set of all points on the ellipse $x^2+9y^2=144$. These two intersect at four points P, Q, R and S. Hence, $A∩B$ contains four points.
