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问题: 初二数学提

3^(x-2)=a,3(x-2)=b,求3(x-y)的值

解答:

3^(x-2)=a ① 3^(y-2)=b ②
①/②得到 (指数相减)
3^(x-y)=a/b ==> (x-y)=log3(a/b) 3是下标,a/b是上标
∴3(x-y) = 3log3(a/b) = 3log3(a)-3log3(b)