Question

PLEASE HELP!!
solve the equation
(e^x-81e^-x)/2 =9

which is the solution in terms of natural logarithms?
x=__________
OR
there is no solution

what is the decimal approximation for the solution?
x=______________
OR
There is no solution

Answer 1

\[
e^x-81e^{-x}=18\\
e^x-{81\over e^x}=18\\
e^{2x}-81=18e^x\\
e^{2x}-18e^x-81=0
\]
substitute \(u=e^x\)
solve for "u"
then find "x"

Answer 2

would it be 9?

Answer 3

would what be 9?

Answer 4

u=9

Answer 5

how will you do the e^x=9

Answer 6

if the question is correct, there'd be no solutions!
check by pluggin in "u=9"

Answer 7

check if the second e^-x is positive or negative...

Answer 8

9 dosent work

Answer 9

so u=9 not is right because there is -81 and not +81 inside quadratic equation

Answer 10

exactly!

Answer 11

check the question

Answer 12

yes I just saw that.

Answer 13

saw what? did you have the question wrong?

Answer 14

lol no saw that 9 doesnt work

Answer 15

yep.
so, no REAL solutions exist.

Answer 16

okay thank you very much!!

Answer 17

yer welcome very much.