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U Unco Senior Member Joined Jul 21, 2005 Messages 1,134 Oct 21, 2005 #2 10(log(0.15x + 1)) + 2.7 = - 10 (log(0.75x + 1)) + 13 Group like terms: 10(log(0.15x + 1)) + 10 (log(0.75x + 1)) = 13 - 2.7 Divide through by 10, and use the log rule log(a) + log(b) = log(a*b): log [(0.15x + 1)*(0.75x + 1)] = 1.03 If the logs are base 10 then take 10 to the power of both sides. Solve the quadratic (0.15x + 1)*(0.75x + 1) = 10^1.03 Take just the positive root only as we cannot take the log of a negative number. Edit: fixed some rhetoric.
10(log(0.15x + 1)) + 2.7 = - 10 (log(0.75x + 1)) + 13 Group like terms: 10(log(0.15x + 1)) + 10 (log(0.75x + 1)) = 13 - 2.7 Divide through by 10, and use the log rule log(a) + log(b) = log(a*b): log [(0.15x + 1)*(0.75x + 1)] = 1.03 If the logs are base 10 then take 10 to the power of both sides. Solve the quadratic (0.15x + 1)*(0.75x + 1) = 10^1.03 Take just the positive root only as we cannot take the log of a negative number. Edit: fixed some rhetoric.
