We are doing logarithms, and I have no examples of problems like this, and have no idea how to do it. I believe you'd take the log of both sides....then I got nuthin. Any assistance is appreciated.
2007-11-20 18:54:07 · 3 answers · asked by C F 1 in Science & Mathematics ➔ Mathematics
You both are great! Thanks a lot!
2007-11-20 19:43:03 · update #1
What troubles me is that I feel that brackets are missing?
Could question be:-
4^(x + 3) = 7^(x - 1)
(x + 3) log 4 = (x - 1) log 7
(x) log 4 + 3 log 4 = (x) log 7 - log 7
3 log 4 + log 7 = (x) (log 7 - log 4)
x = (3 log 4 + log 7) / (log 7 - log 4)
x = 10.9
PS
Any base may be used when taking logs.
2007-11-21 02:01:59 · answer #1 · answered by Como 7 · 2⤊ 1⤋
4^x+3 = 7^x-1
log both sides when bring the exponents to the front of log making it
(x+3)log4=(x-1)log7
distribute.
xlog4+3log4=xlog7-log7
move all xlogs to one side.
xlog4-xlog7=-log7-3log4
common factor x
x(log4-log7)=-log7-3log4
divide to get x by itself.
x=(-log7-3log3)/(log4-log7)
2007-11-20 19:01:35 · answer #2 · answered by kuyaERiC 2 · 0⤊ 1⤋
Take natural log,
(x+3)ln4 = (x-1)ln7
Solve for x,
x = (3ln4 + ln7)/(ln7 - ln4)
2007-11-20 18:56:57 · answer #3 · answered by sahsjing 7 · 2⤊ 0⤋