Scott,

Make up two columns, one with your xvalues (let's say, from A2 down), the other with the formula

=m*A2+b

where A2 is the first of your xvalues. Substitute m and b with values or cell references - like $C$2

Then copy that formula down, and graph based on that table.

HTH,
Bernie
MS Excel MVP

Decide on your minimum & maximum X values for your graph, & put them in
consecutive cells in a column (perhaps A2 & A3).  Use your formula to
generate corresponding Y values in the next column (B2 and B3).
To aid in plotting the graph, put a heading (Y, or whatever) at the top of
your Y column but leave the corresponding heading blank at the top of the X
column.  Select the 2 columns, including the Y heading and the blank above
the X (A1:B3), Insert/ Chart/ XY (select the subtype with straight line and
no point markers, if that's what you want), Series in columns, ...  other
options to suit.
-
David Biddulph

G'day Scott,

You're not by any chance a soil tester from Australia are you?