How do you solve #23^x + 5 = 128#? Precalculus Solving Exponential and Logarithmic Equations Logarithmic Models 1 Answer sente Oct 3, 2016 #x = ln(123)/ln(23) = log_23(123)~~1.535# Explanation: Using the property that #ln(a^x) = xln(a)#, we have #23^x+5 = 128# #=> 23^x = 123# #=> ln(23^x) = ln(123)# #=> xln(23) = ln(123)# #:. x = ln(123)/ln(23) = log_23(123)~~1.535# Answer link Related questions What is a logarithmic model? How do I use a logarithmic model to solve applications? What is the advantage of a logarithmic model? How does the Richter scale measure magnitude? What is the range of the Richter scale? How do you solve #9^(x-4)=81#? How do you solve #logx+log(x+15)=2#? How do you solve the equation #2 log4(x + 7)-log4(16) = 2#? How do you solve #2 log x^4 = 16#? How do you solve #2+log_3(2x+5)-log_3x=4#? See all questions in Logarithmic Models Impact of this question 1237 views around the world You can reuse this answer Creative Commons License