急.Maths!Thanks!化简下列各项:(请列步骤)1). 8(3^n) - 5(3^n-1) / √9^n + 3^n-22). 3 ㏒ x + ㏒ y^4 / 2^-3 ㏒ x^3 + ㏒ √y...Thank!^^

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急.Maths!Thanks!
化简下列各项:(请列步骤)
1). 8(3^n) - 5(3^n-1) / √9^n + 3^n-2
2). 3 ㏒ x + ㏒ y^4 / 2^-3 ㏒ x^3 + ㏒ √y
...Thank!^^

第一题:
8(3^n) - 5(3^n-1) / √9^n + 3^n-2
= [8*3^n-(5/3)*3^n]/[3^n-(1/9)*3^n]
=[(8-5/3)*3^n]/[(1+1/9)*3^n]
=(19/3)/(10/9)
=5.7
第二题:
3 ㏒ x + ㏒ y^4 / 2^-3 ㏒ x^3 + ㏒ √y
=log x^3 + log y^4*8-3 log x^3 + log y^1/2
=-6 logx + 64/2 logy

8(3^n) - 5(3^n-1) / √9^n + 3^n-2
= [8*3^n-(5/3)*3^n]/[3^n-(1/9)*3^n]
=[(8-5/3)*3^n]/[(1+1/9)*3^n]
=(19/3)/(10/9)
=57/10=5.7
3 ㏒ x + ㏒ y^4 / 2^-3 ㏒ x^3 + ㏒ √y
看不明白你的式子

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