SOLUTION: Graph a parabola with axis of symmetry x = 0, an x-intercept at x = 7, and y-intercept at y=3.

Since x= 0 is the axis of symmetry, with x-interception x= 7, the parabola has 
second x-interception at symmetric point x= -7.


So, the parabola has the form

    y = a*(x-7)*(x+7 = a*(x^2-49),


where "a" is an unknown real coefficient.


Find it from the condition  y = 3  at  x = 0

    a*(0^2-49) = 3,

    -49a = 3,

       a = .


Thus the equation for the parabola is  y = .


To get the graph, go to website

    www.desmos.com/calculator

find there free of charge online plotting tool for common use,
print there the found equation of the parabola  and obtain 
the desired plot in the next instance.