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+(a−b)=a−b
−(a+b)=−a−b
−(a−b)=−a+b
總結：當括弧前為+，則去括號後不變；若括弧前為−，則去括弧後須變號(+變−、−變+)
說到任何數X0，讓我想到任何數÷0，趨近無限和無解，本人尚不清楚現今學術上的正解，但我個人是比較偏好無解(無意義)這個答案，但之前也曾聽過能÷0這種說法。以1÷0=？為例，驗算回去：？×0=1，？=...
parenting.com.tw/article/5089631
我覺得挺有道理 (就是解答你上面留言最後一句的疑問)，小朋友也容易理解～