Sonia, here is an illustration for the graph of y = f(x) = x^3 - 5x^2 - 5x + 3 and the corresponding graph y = f(|x|). Observe that the right half of the red (original) graph overlaps with the new f(|x|) graph, whereas the left hand of the red graph is discarded, and taking its place is a reflected graph. The line of symmetry is the y-axis itself.