How does the graph of the function h(x)=3x^2 different from the graph of the function f(x)=x?

The graph of h(x) = 3x^2 is a curved "bowl" like shape that opens upward. The curve is called a parabola. The two ends go on forever upward. It has symmetry along the y axis. 

In contrast, the graph f(x) = x is a straight line that goes through (0,0) and (1,1). This is known as a linear equation. 

First one is 1 second one is 3