Question

Solve the logarithmic equation for . Please round the answer to four decimal places, if necessary.
ln(x-4)+ln(x+5)=1

Answer 1

Reason I'm confused is because unlike log, in ln the exponential form is e^y=x and I'm having trouble solving the rest

Answer 2

ln(a) + ln(b) = ln(ab)

Answer 3

That's x^2+x-20?

Answer 4

yep.

now, ln(0) = 1 because e^0 = 1

Answer 5

and also any number to the 0 power except 0 is 1

Answer 6

your equation is really:

x^2 +x - 20 = 0

Answer 7

wait!

Answer 8

or

(x-4) (x+5) = 0

Answer 9

e^1=e

Answer 10

we have (x-4)(x+5)=e

Answer 11

lol..... maybe it does, and maybe it doesnt :)

Answer 12

yes myininaya

Answer 13

if we do it like amistre we would make the problem much easier but also kindof wrong

Answer 14

and kindof wrong is just wrong

Answer 15

now im confused >_<

Answer 16

horseshoe and handgranades me friend :)

Answer 17

so we have x^2-9x+20+e=0

Answer 18

oops -e

Answer 19

wouldnt it be -e?

Answer 20

Yes i blame amistre

Answer 21

lol

Answer 22

bring over 1 to the left at the start...before changinglg form...

Answer 23

...its my liver pills...blame the liver pills :)

Answer 24

so whats the answer?

Answer 25

use quadractic formula x=(9@sqrt(81-4(1)(20-e))/2 where @ means + or -, but make sure your answer is positive because you cannot do ln(negative)

Answer 26

sorry...doesn't make a difference what I said

Answer 27

Quadratic formula the way to go

Answer 28

this is what i put on the formula
-1+squareroot(1^2 -4(1)(20-e))))/2

Answer 29

no

Answer 30

a=1 n=-9 c=20-e correct?

Answer 31

c=-20-e

Answer 32

b=-9*

Answer 33

b=1

Answer 34

no b =1

Answer 35

dont listen to me

Answer 36

im doing two things at once sorry

Answer 37

my calculator wont work

Answer 38

(-1+sqrt(1-4(-20-e))/2=4.2925 and (-1-sqrt(1-4(-20-e))/2=-5.2925 but we can't use -5.2925 since it is negative and the natural log of a negative number doesnt exist

Answer 39

x can be negative if it is not the only thing controling the value of the log.

the thing is:

x-4 needs to be greater than 0 and,
x+5 needs to be greater than 0.

x >4 serves both cases.

Answer 40

correct!

Answer 41

that negative number gives you another negative number when you plug it into x-4