Intro to the imaginary unit i

This puzzle can be given anytime after students have learned that \(i^2 = -1.\) However, I wouldn't give this puzzle immediately after introducing \(i,\) as looking for occurences of \(i\) is pretty much a dead give-away.


Make the equation true by adding or removing 4 dots. Note that a + sign must consist of 3 horizontal and vertical dots, and a minus sign must consist of 4 horizontal dots:

Solution