precal
posted by sonia .
what is the vertex and directrix of the parabola y=1/2x^2 + 10  46

I'm assuming your equation is this:
y = 1/2x^2 + 10x  46
The above equation would then be in the format:
y = ax^2 + bx + c
...where a, b, and c are the coefficients of each term in this format.
Therefore, in your equation, a = 1/2, b = 10, and c = 46
To find the vertex, use this:
b/2a for x
(4ac  b^2)/4a for y
You can also find y by substituting the value for x into the equation and solving for y.
Vertex will be in the format (x,y).
I'll let you take it from here.