Ctrl+Alt+"+"
 

Could somebody please suggest me how to make "ctrl alt +" and "ctrl alt -" work on a linux laptop. What I meant is that as there is no numeric keypad on laptop, so how to map "+" and "-" so that it gives the same functionality as pressing "ctrl alt +" for a desktop user.

Thanks.

usually there is a key called "FN" on laptop keyboards
you can use it to activate the "keypad"

press and hold FN, find the "+" key (often color coded blue) on your keyboard and press it to get the "keypad +" key

You should also be aware that some, usually older, laptop LCDs won't support differing resolutions all that well. You may find that when you change it, the visible area doesn't take up the entire screen and you'll end up with a border around the visible area.