Exercises 19-21 In Exercises 19-29, evaluate each expression without using a calculator. If evaluation is not possible, state the reason. 19. log, 64 20. logs 23 21. log3(-9) Exercises 50-51, 54-55 In Exercises 50-53, use properties of logarithms to expand each logarithmic expression as much as possible. Where possible, evaluate logarithmic expressions without using a calculator. 50. log,(36x3) 51. log4 64 In Exercises 54-57, use properties of logarithms to condense each logarithmic expression. Write the expression as a single logarithm whose coefficient is 1. 54. log, 7 + log; 3 55. log 3 - 3 log x Exercises 64-67, 71-72 In Exercises 64-73, solve each exponential equation. Where necessary, express the solution set in terms of natural or common logarithms and use a calculator to obtain a decimal approximation, correct to two decimal places, for the solution. 64. 24-2 = 64 65. 125* = 25 66. 10* = 7000 67. gr+2 = 27-* 71. 54+2 = 37,500 72. 3*+4 = 72x-1