The directrix of the parabola is 
<h3>How to determine the equation of the directrix?</h3>
The parabola equation is given as:

A parabola is represented as:

By comparing both equations, we have:
4p = 1/4 ==> p = 1/16
-k= 3 ==> k = -3
The directrix is represented as:
y = k - p
So, we have:

Take the LCM

Evaluate

Hence, the directrix of the parabola is 
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We know that
Applying the Pythagoras Theorem
c=²=a²+b²
where c is the diagonal of the wall
a=12 ft
b=6 ft
c²=12²+6²-----> c²=144+36-----< c²=180-----> c=√180------> c=6√5 ft
the answer is
<span>the exact length of the brace is 6</span>√5 ft
I dont even know what your asking
A is 31,570 got it right on my test