Inernal function for finding y

[Lamb Chop]

I have two points, (x1, y1) and (x2, y2)

Is there an internal function that can calculate the value of y for a
particular x?

Or do I need to establish the linear equation from finding slope and
intersection points, then substitute the new x into it?

Thanks

 

[JE McGimpsey]

One way:

See FORECAST() in XL Help