The examples below assume that you know at least two points (x1,y1) and (x2,y2) and want to solve for y given x based on the equation for a line: y=mx+b, where m is the slope and b is the y-intercept.
1. Using the Point-Slope formula, where the slope is (y2-y1)/(x2-x1):
2. Using the SLOPE and INTERCEPT functions to solve for m and b:
3. The TREND function uses linear regression to solve for y if you have two or more points. This is also a way to estimate y from a linear fit of many points.