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解:原式 = (8/9) * (3/4 - 7/16 + 1/4)
= (8/9) * (1 - 7/16)
= (8/9) * (9/16)
= 1/2
= (8/9) * (1 - 7/16)
= (8/9) * (9/16)
= 1/2
追问
为什么变成了1-16分之7
追答
解:原式 = (8/9) * (3/4 - 7/16 + 1/4) ←(拆小括号)
= (8/9) * (3/4 + 1/4 - 7/16) ←(加法交换律)
= (8/9) * (1 - 7/16) ←(3/4 + 1/4 = 1)
= (8/9) * (9/16)
= 1/2
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