Question

what is the solution to In(a+3)=In(a-3)=In16

Answer 1

Is it +/- in the middle of those "ln" operators?

Answer 2

if it is + in the middle then,
ln((a+3)(a-3))=ln16
a^2-9=16
a^2=25
a= +5 or - 5

Answer 3

a can't be -5 because then ln(a-3) will be undefined.

Answer 4

thank you

Answer 5

@GT , you are right. Sorry I am liitle sleepy :P

Answer 6

also if 3^2x=100 then to the nearest tenth what does x =

Answer 7

aply log on both sides and then apply power rule

Answer 8

how would you do that?

Answer 9

log ( 3^(2x))= log (10^2)

POwer rule is
\[\log_{a}b^c = c \log_{a}b\]

therefore
(2x)log 3 = 2 log10
x= log 10 / log 3

Answer 10

Thank you again

Answer 11

Welcome :)

Answer 12

the amount of a 10 miligram dose of drug remaining in the body is given by the formula 10(.8)^t. Find the nearest 10th of an hour how long it takes for half of the drug dose to leave the body

Answer 13

hello

Answer 14

10(0.8)^t = 0.5
(0.8)^t= 0.05
Applying log on both sides
t*log(0.8)=log(0.05)
t= log(5*10^(-2))/log (8 * 10^-1)
t=(log(5)-2log10) / (log(8) - 1 *log(10)
t=(log (5) - 2) / ( log (8) - 1)

Answer 15

@rama1010 , next time ask separately . Not in this thread :)

Answer 16

ok but what would be the answer in decimal form

Answer 17

Use calculator please and find the log values :). Substitute and simplify

Answer 18

thank you very much for all your help. I am very grateful!!!

Answer 19

however i still can't seem to find the actual values

Answer 20

sorry?
log 5 =0.698970004
log 8 = 0.903089987

Now substitute and simplify :)

Answer 21

the answer is .777 right