ln (5x + 5) - 1 = ln (x - 4)?

4 ⤊

ln (5x + 5) - 1 = ln (x - 4)?

x = ????

2007-11-28 16:56:56 · 2 answers · asked by J S 1 in Science & Mathematics ➔ Mathematics

2 answers

ln (5x + 5) - ln (x - 4) = 1
ln [(5x + 5) / (x - 4) ] = 1
(5x + 5) / (x - 4) = e
5x + 5 = e (x - 4)
5x + 5 = e x - 4e
(5 - e)x = - 4e - 5
x = - (4e + 5) / (5 - e)
x = - 6.96

2007-11-29 02:15:01 · answer #1 · answered by Como 7 · 3⤊ 1⤋

ln(5x+5) - ln(x-4) = 1
ln[(5x+5)/(x-4)] = 1
[(5x+5) / (x-4)] = e
5x+5 = x*e - 4*e
x(5-e) = -4*e - 5
x = -(4*e+5)/(5-e), but this is a negative number, and ln(u) is only defined for u>0. Since x-4<0, there is no solution. Sure you typed the problem correctly?

2007-11-29 01:06:16 · answer #2 · answered by halac 4 · 1⤊ 1⤋