Notice the difference: there's a plus sign here;there's a minus sign here.

注意这里的不同：,上面是加号，这里是减号。

youdao

Because it's this plus that that's equal to zero, and there's the minus sign that I forgot to write down.

因为这个加上这个等于零，这里我忘写了一个负号。

youdao

Because it's this plus that that's equal to zero, and there's the minus sign that I forgot to write down.

因为这个加上这个等于零，这里我忘写了一个负号。

youdao