General equation of a parabola:
[tex](x-h)^2=4p(y-k)[/tex]
Equation of the axis of symmetry:
x = h
In this case, the axis of symmetry is x = 2, then h = 2.
Equation of the directrix:
y = k - p
In this case, the equation of the directrix is y = -9/4, then:
-9/4 = k - p (eq. 1)
Equation of the focus:
F(h, k+p)
In this case, the coordinates of the focus are (2,-7/4), then:
-7/4 = k + p (eq. 2)
Adding equation 1 to equation 2:
-9/4 = k - p
+
-7/4 = k + p
--------------------
-4 = 2k
(-4)/2 = k
-2 = k
Substituting this result into equation 2 and solving for p:
-7/4 = -2 + p
-7/4 + 2 = p
1/4 = p
Substituting with h = 2, k = -2, and p = 1/4 into the general equation, we get:
[tex]\begin{gathered} (x-2)^2=4\cdot\frac{1}{4}(y-(-2)) \\ (x-2)^2=y+2 \end{gathered}[/tex]
