Let R={(x,y):x,y∈R,x2+y2≤25}  R'={(x,y):x,y∈R,y≥(4/9)x2}  then

The equation x2+y2=25  represent a circle with centre (0,0)  and radius 5 and the equation y=49x2  represent a parabola with vertex (0,0)  and focus (0,916). Hence R∩R'  is the set of points indicated in the Fig.={(x,y):−3≤x≤3,0≤y≤5}.Thus dom R∩R'=[−3,3]  and range  R∩R'=[0,5]⊃[0,4]Since (0,0)∈R∩R'  and (0,5)∈R∩R'Hence R∩R'  doesn’t defines a function.