Shape of y=x^2, shifted 3 units to the right and 7 units down.

In a quadratic function of the form ax^2+bx+c, which of the following is not true? a. the y-intercept is c. b. if a is positive, the parabola opens up. c. the vertex has an x-coordinate of -b/2a. d. the axis of symmetry is the line y=-b/2a.