化简:7+4-[3-{1+2-(4-9)}]
已知条件 7+4-[3-{1+2-(4-9)}]
求解:我们要求出 7+4-[3-{1+2-(4-9)}] 的值
解:
7 + 4 - [3 - {1 + 2 - (4 - 9)}]
= 7 + 4 - [3 - {1 + 2 - (- 5)}]
= 7 + 4 - [3 - {1 + 2 + 5}]
= 7 + 4 - [3 - {8}]
= 7 + 4 - [3 - 8]
= 7 + 4 - [- 5]
= 7 + 4 + 5
= 16
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