解方程 3^x - 3^-x = 80/9

来源:学生作业帮助网 编辑:作业帮 时间:2024/11/29 21:24:49
解方程 3^x - 3^-x = 80/9
x){|i;V0P 6IEx l0aݾ[]I PPD.bYg0IY5,K 55Jt-5"O;J [K @ [#<;km[S}c3l2``صb=Z@K+@43@rcLiY}/z@BP[q8U՛

解方程 3^x - 3^-x = 80/9
解方程 3^x - 3^-x = 80/9

解方程 3^x - 3^-x = 80/9
设t=3^x
3^x - 3^-x = 80/9
t - 1/t =80/9
9t^2 - 80t - 9=0
(9t+1)(t-9)=0
又t>0
t=9
3^x=9=3^2
x=2

X=5/36

3^x=9
X=2

3^x - 3^-x = 80/9
(9*3^2x+1)(3^3x-9)=0
则9*3^2x+1=0或3^3x-9=0
从而3^3x=9
x=2

x=2