Answer
(a) Not function of $x$
(b) Function of $x$
Work Step by Step
(a) The graph is not a function of $x$ because there are vertical lines that intersect the curve twice. And we know that in order for it to be a function, each $x$ must have an unique output, but in this case where the vertical line intersects twice, it indicates that the $x$ value has two different $y$ value outputs.
(b) There is no vertical lines intersecting the graph more than once, hence each $x$ value only has one $y$ value output. Therefore this is a function.
