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(490+687×492/493×687-197)-1/2005用简便运算
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(490+687×492/493×687-197) - 1/2005
用简便运算
用简便运算
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(490+687×492)/(493×687-197) - 1/2005
=[490+687×(490+2)]/[(490+3)×687-197] - 1/2005
=(490+687×490+2×687)/(490×687+3×687-197) - 1/2005
=(687×490+1864)/(687×490+1864)- 1/2005
=1-1/2005
=2004/2005
对的
=[490+687×(490+2)]/[(490+3)×687-197] - 1/2005
=(490+687×490+2×687)/(490×687+3×687-197) - 1/2005
=(687×490+1864)/(687×490+1864)- 1/2005
=1-1/2005
=2004/2005
对的
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