推 seame:太強了啦~~我都想不出來^^a 10/03 17:53
49x28 = (24x2+1)x28
= 24x(2x28) + 28
= (12x2)x56 + 28
= 12x112 + 28
= (6x2)x112 + 28
= 6x224 + 28
= (3x2)x224 + 28
= 3x448 + 28
= (1x2+1)x448 + 28
= 896 + 448 + 28
= 1372
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