Adding two Functions point by point
Author: Scott Farrar

Drag the point on the x axis to observe how
f(x) + g(x) can be created point by point.

f(x) + g(x) can be shown as the sum of each pair of points
that have the same x coordinate.

B is on f(x),   C is on g(x)
So, the cooresponding y value for D, on f+g, is
the sum of the y values of B and C.

(Observe the y values of B, C and D on the graph)

DragMe = Point(xAxis)
a = OrthogonalLine(DragMe, xAxis)
f(x) = x^(2) - 4
B = Intersect(f, a)
g(x) = 2 x + 4
C = Intersect(g, a)
D: (x(DragMe), y(B) + y(C))
b = Segment(DragMe, B)
c = Segment(DragMe, C)