S sarav7 New member Joined Dec 6, 2011 Messages 1 Dec 6, 2011 #1 1/3(6)^(-4x)+1=6 I got an answer, but checked it in the back of the book and it was wrong. Here is what I did: 1/3(6)^(-4x)=5 6^-4x=15 log base 6 of 15 =-4x log6/log15=-4x -.165=x The right answer is -.378
1/3(6)^(-4x)+1=6 I got an answer, but checked it in the back of the book and it was wrong. Here is what I did: 1/3(6)^(-4x)=5 6^-4x=15 log base 6 of 15 =-4x log6/log15=-4x -.165=x The right answer is -.378
M Mrspi Senior Member Joined Dec 17, 2005 Messages 2,116 Dec 6, 2011 #2 sarav7 said: 1/3(6)^(-4x)+1=6 I got an answer, but checked it in the back of the book and it was wrong. Here is what I did: 1/3(6)^(-4x)=5 6^-4x=15 log base 6 of 15 =-4x log6/log15=-4x -.165=x The right answer is -.378 Click to expand... Ok...what you have is correct to this point: 6-4x = 15 Now, how about taking the log of both sides (I'll use natural logs): ln 6-4x = ln 15 Use one of the rules of logs: ln bn = n ln b (-4x) ln 6 = ln 15 x * -4 ln 6 = ln 15 Divide both sides by (-4 ln 6): x = ln 15 / (-4 ln 6)
sarav7 said: 1/3(6)^(-4x)+1=6 I got an answer, but checked it in the back of the book and it was wrong. Here is what I did: 1/3(6)^(-4x)=5 6^-4x=15 log base 6 of 15 =-4x log6/log15=-4x -.165=x The right answer is -.378 Click to expand... Ok...what you have is correct to this point: 6-4x = 15 Now, how about taking the log of both sides (I'll use natural logs): ln 6-4x = ln 15 Use one of the rules of logs: ln bn = n ln b (-4x) ln 6 = ln 15 x * -4 ln 6 = ln 15 Divide both sides by (-4 ln 6): x = ln 15 / (-4 ln 6)
