getting a y-value from a graph knowing the corresponding x-value

[lsu-i-like]

if you have a graph with three points plotted [(x1,y1),(x2,y2),(x3,y3)],
can excel find y4 if you know the corresponding x4?

 

[Jerry W. Lewis]

You could use FORECAST() or TREND() to predict the y-value assuming that
the points can be approximated by a straight line. You could use
FORECAST() to predict the y-value assuming that the points can be
approximated by a quadratic.

Jerry