document.write( "Question 113487: simplify log1 -3 log2 + log16 \n" ); document.write( "
Algebra.Com's Answer #82551 by bucky(2189)![]() ![]() ![]() You can put this solution on YOUR website! First recognize that log(1) = 0. [This is true regardless of what base logarithm is used.] \n" ); document.write( ". \n" ); document.write( "Next, work on -3*log(2). By the rules of logarithms, the multiplier of a logarithm (in this \n" ); document.write( "case that multiplier is -3) can become the exponent of the quantity that the log is operating \n" ); document.write( "on. That is to say -3*log(2) is equivalent to log(2^(-3)). But 2^(-3) equals 1/(2^3) by \n" ); document.write( "the rules of exponents. And 1/(2^3) = 1/8 when you cube 2. Therefore, -3*log(2) converts to \n" ); document.write( "log(1/8). \n" ); document.write( ". \n" ); document.write( "At this point the original problem has been converted to: \n" ); document.write( ". \n" ); document.write( "0 + log(1/8) + log(16) \n" ); document.write( ". \n" ); document.write( "and the zero can be dropped so that the problem is just: \n" ); document.write( ". \n" ); document.write( "log(1/8) + log(16) \n" ); document.write( ". \n" ); document.write( "Recognize now that by the rules of logarithms the sum of two logarithms is equal to the \n" ); document.write( "log of their product. Applying this rule to the problem results in: \n" ); document.write( ". \n" ); document.write( "log(1/8) + log(16) = log((1/8)*16) = log(16/8) = log(2) \n" ); document.write( ". \n" ); document.write( "The answer to the problem is log(2) \n" ); document.write( ". \n" ); document.write( "You can check this answer by using a scientific calculator as follows: \n" ); document.write( ". \n" ); document.write( "a) Return to the original problem. Use the calculator to find log of 1. You should get zero \n" ); document.write( "as the answer to that part of the problem. \n" ); document.write( ". \n" ); document.write( "b) Use the calculator to find the base 10 log of 2. The answer to that should be 0.301029995. \n" ); document.write( "Multiply that by -3 and you should have -0.903089987 \n" ); document.write( ". \n" ); document.write( "c) Use the calculator to find the base 10 log of 16. You should get 1.204119983 \n" ); document.write( ". \n" ); document.write( "d) Total all the results ... 0 - 0.903089987 + 1.20411983 = 0.301029995 \n" ); document.write( ". \n" ); document.write( "That's the result of working the problem. But we found that log(2) should be equivalent \n" ); document.write( "to that. So use the calculator to find the base 10 log of 2 and you will see that it \n" ); document.write( "indeed is 0.301029995 ... which verifies that log(2) is equivalent to the original problem. \n" ); document.write( ". \n" ); document.write( "Hope this helps you to see your way through this problem and to understand the rules of \n" ); document.write( "logarithms and exponents a little better. \n" ); document.write( ". \n" ); document.write( " \n" ); document.write( " |