4.3.3  Manipulating subexpressions

If a subexpression is selected in the expression editor, then any menu command will be applied to that subexpression.

For example, suppose that you enter the expression

in the expression editor. Note that you can use the abilities of the editor to make this easier. First, enter x+1. Select this with the up arrow, then type * followed by x+2. Select the x+2 with the up arrow and then type * followed by x-1. Using the up arrow again will select the x-1. Select the entire expression with the up arrow, and then select eval from the M menu. This will put all factors at the same level. Suppose you want the factors (x+1)*(x+2) to be expanded. You could select (x+1)*(x+2) with the mouse and do one of the following:

• Select the Expression▸Misc▸normal menu item. You will then have normal((x+1)*(x+2))*(x-1) in the editor. If you hit enter, the result (x² + 3x + 2)*(x−1) will appear in the output window.
• Select the Expression▸Misc▸normal menu item, so again you have normal((x+1)*(x+2))*(x-1) in the editor. Now if you select eval from the M menu, then the expression in the editor will become the result (x² + 3x + 2)*(x−1), which you can continue editing.
• Choose normal from the M menu. This will apply normal to the selection, and again you will have the result (x² + 3x + 2)*(x−1) in the editor.

There are also keystroke commands that you can use to operate on subexpressions that you’ve selected. There are the usual Ctrl+Z and Ctrl+Y for undoing and redoing. Some of the others are given in the following table.