Logarithm?

👨🏻‍🏫 學術台數學

john ng

2016-11-10 10:10 am

Logarithm?
1.Slove (2^2x)(3^3y)=31.4 and (5^5x)(7^7y)=36.6 x=? y=?
2.Slove 5(2x)=3^y and x^2+y = 27.5
X1=
Y1=
X2=
Y2=
3.Slove 259-18.4（e^x/a+e^-x/a)
If a=34.8 and y=217.44 x=?

更新1:

3.The height of an arch is y = 259-18.4（e^x/a+e^-x/a) If a=34.8 and y=217.44 x=?

回答 (1)

pui

2016-11-10 11:16 am

✔ 最佳答案

1.
(2^2x)(3^3y)=31.4
(x log 2^2)+(y log 3^3)=log 31.4
(5^5x)(7^7y)=36.6
(x log 5^5)+(y log 7^7)=log 36.6
x=-4.592892308
y=2.977668192

2
5(2^x)=3^y
log 5+(x log 2)=y log 3
(x log 2)-(y log 3)=-log 5
x^2+y = 27.5
x1=4.796730793
x2=-5.427660547
y1=4.491373698
y2=-1.95949901

3.
我不知道是打錯了方程或是打少了東西的，所以不能幫你計算。

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