How would you solve this problem?

Show that Max |G(x)| = h^(2)/4

xj<=x<=x(j+1)

Where G(x) = (x-jh)(x-(j+1)h)

j = iteration number

h = step size

At first I realize that

xj = j * h

x(j+1) = (j+1) * h

but I still can't reach the final answer h^(2)/4

Help Please!!