And again, if we write out what all the terms are, we again have 1 s a squared plus 1 s b squared, but now what we're doing is we're actually subtracting the interference term.

同样，如果我们把所有的项都写出来，同样我们有1s平方加上1sb平方，先现在我们做的是,我们要减去干涉项。