Answer:
ac is parallel to df because it doesn't intersect with each other
Answer:
In a quadratic equation of the shape:
y = a*x^2 + b*x + c
we hate that the discriminant is equal to:
D = b^2 - 4*a*c
This thing appears in the Bhaskara's formula for the roots of the quadratic equation:

You can see that the determinant is inside a square root, this means that if D is smaller than zero we will have imaginary roots (the graph never touches the x-axis)
If D = 0, the square root term dissapear, and this implies that both roots of the equation are the same, this means that the graph touches the x axis in only one point, wich coincides with the minimum/maximum of the graph)
If D > 0 we have two different roots, so the graph touches the x-axis in two different points.
Well the centroid is the point that connects the median of a side with the opposite vertex. This means that each line is split i half. Notice that line HG is split in half by point K. that means that each of the segments that K splits is equal. so we know
HK = KG
and we know
HK = 3x
KG = x + 8
since
HK = KG then
3x = x + 8
2x = 8
x = 4
now we have x. we know that the each line that runs from a midpoint to a vertex is seperated by the centroid. the 2 line segments are a 2:1 ratio. so
2*JL = 1LG
we know
JL = x + 3
so
2 * (4 + 3) = LG
LG = 14