若3^x=4,3^y=6,求9^2x-y+27^x-y

来源：学生作业帮编辑：作业帮分类：数学作业时间：2024/05/11 17:34:40

9^2x-y+27^x-y
=9^2x÷9^y-27^x÷27^y
=3^4x÷3^2y-3^3x÷3^3y
=(3^x)^4÷(3^y)^2-(3^x)^3÷(3^y)^3
=256÷36-64÷216
=184/27
再问： 9的2x-y+27的x-y =3^（4x-2y)+3^(3x-3y) =3^4x×3^(-2y)+3^3x×3(-3y) =4^4×6^(-2)+4^3×6^(-3) =200/27 这个错了吗
再答：哦，对不起，我算错了前面都对的就是最后一步=200/27

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