Consider the following four standard parabolas:
(A) y2=4ax, (B) y2=−4ax, (C) x2=4ay, (D) x2=−4ay, where a>0 in every case.
Answer the questions below, writing each response with brief justification.
(i) For each equation, state whether its axis is horizontal or vertical.
(ii) For each equation, determine whether the parabola opens to the right, left, upward, or downward.
(iii) Write the coordinates of the focus for every equation and specify the exact quadrant or axis on which the focus lies.