Tính nhanh: 217 + [43 + (-217) + (-23)]
Giải thích
217 + [43 + (–217) + (–23)]
= 217 + 43 + (–217) + (–23)
= [217 + (–217)] + [43 + (–23)]
= 0 + 20 = 20.
217 + [ 43 + (–217) +(–23)].
217 + [43 + (–217) + (–23)]
= 217 + 43 + (–217) + (–23)
= [217 + (–217)] + [43 + (–23)]
= 0 + 20 = 20.
217 + [ 43 + (–217) +(–23)].