题目内容
(6分) 已知a、b互为相反数，c、d互为倒数，
，
求代数式：
的值．
，求代数式：
的值．的值为1或– 7解：由题意得：a + b = 0，cd = 1，
············································· 2分
①当m = 2时，原式
··········································· 4分
②当m =" –" 2时，原式
∴···································································· 6分
············································· 2分①当m = 2时，原式
··········································· 4分②当m =" –" 2时，原式
∴
···································································· 6分
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