Reconnaître si une relation dont on connaît la représentation graphique est une fonction

A coordinate plane. The x- and y-axes both scale by one. There is a graph of a curve. The curve increases at a non linear rate from the point negative eight, one-half to negative five and one-half, eight and one-half. Then it decreases at a non linear rate to the point negative one and one-half, one-half. Then it increases at non linear rate to the point one and one-half, eight and one-half. Then it decreases at a non linear rate to the point four and one-half, one-half. Then it increases at a non linear rate to seven and one-half, eight and one-half. All of these values are estimated.