Using a Trendline formula to get Values for any given X in Excel

You would use the linest() function, which retus an array. We use the INDEX() to pull the individual parts of the array:

=(INDEX(LINEST($B$2:$B$6,$A$2:$A$6),1,1)*D2)+INDEX(LINEST($B$2:$B$6,$A$2:$A$6),1,2)

D2 contains my x of .1. So I put this in E2 and copied down.