How to Graph Linear Equations and Problems

A linear equation is an equation in which there are no squares, cubes or higher powers. A set of linear equations can include two or more variables, but if there are more than two variables, it is very hard to graph them, and if there are more than three variables it is impossible, as each variable requires a dimension.



Graphing a linear equation gives a graphical feel for how the equation works. Graphing two or more equations can also show if they are compatible--that is, if there are any values that satisfy all the equations.

• 1

  Enter a header for one variable at the head of a column in Excel (typically column A and cell A1). This header should match the variable on the right side of your equation, typically "X." For example, if you have two equations

  Y = X + 3

  and

  Y = 2X + 5

  and a blank Excel sheet, then enter X in cell A1.

• 2

  Enter the variable on the left side of your equation in the cell to the right of X. If you have more than one equation, enter Y1. In our example, we would enter Y1 in cell B1

• 3

  Repeat for any additional equations. In our example, enter Y2 in cell C1.

• 4

  Enter X values in the column under the X header. These values don't really matter, but if your equations are from some applied field, you may wish to choose realistic values. If not, choose -5 to + 5. In our example, enter these in cells A2 to A12.

• 5

  Enter the first (or only) equation under the next header. In our example, enter =A2+3 in cell B2, then copy this to cells B3 to B12.

• 6

  Repeat Step 5 if there are more equations. In our example, enter =2*A2 + 5 in cell C2, and copy this to cells A3 to A12.

• 7

  Click on "Insert" in an empty cell, then "Scatter," then the graph on the top right (with dots and lines). This will generate graphs for each equation. If there is more than one equation, there will be more than one line, and if there is a point where all the lines cross, then this corresponds to values that solve all the equations.