document.write( "Question 203386: use logarithms to solve each equation:\r
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document.write( "3(superscript x)= 5(superscript 5x-1) \n" );
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Algebra.Com's Answer #153450 by Theo(13342) You can put this solution on YOUR website! 3 (superscript x) is usually referred to as 3^x. \n" ); document.write( "similarly 5 (superscript 5x-1) is usually referred to as 5^(5x-1). \n" ); document.write( "^ is shift 6 on your keyboard. \n" ); document.write( "----- \n" ); document.write( "they should look like the following if I understood you correctly.\r \n" ); document.write( "\n" ); document.write( "----- \n" ); document.write( "as a general rule, if a = b, then log(a) = log(b), so if we let: \n" ); document.write( "a = 3^x, and \n" ); document.write( "b = 5^(5x-1), we get: \n" ); document.write( "log(3^x) = log(5^(5x-1)) \n" ); document.write( "----- \n" ); document.write( "by the rules of logarithms: \n" ); document.write( "since we know, that log(3^x) is the same as x*log(3), \n" ); document.write( "and we know that log(5^(5x-1)) is the same as (5x-1)*log(5), we get: \n" ); document.write( "x*log(3) = (5x-1)*log(5) \n" ); document.write( "----- \n" ); document.write( "if we remove parentheses from the right side of the equation, we get: \n" ); document.write( "x*log(3) = 5x*log(5) - log(5) \n" ); document.write( "----- \n" ); document.write( "if we add log(5) to both sides of this equation, and we subtract x*log(3) from both sides of this equation, we get: \n" ); document.write( "log(5) = 5x*log(5) - x*log(3) \n" ); document.write( "----- \n" ); document.write( "if we separate the common factor x from the right side of the equation, we get: \n" ); document.write( "log(5) = x*(5*log(5) - log(3)) \n" ); document.write( "which looks like this:\r \n" ); document.write( "\n" ); document.write( "if we divide both sides of the equation by (5*log(5) - log(3)), we get: \n" ); document.write( "x = log(5) / (5*log(5) - log(3)) \n" ); document.write( "which looks like this:\r \n" ); document.write( "\n" ); document.write( "----- \n" ); document.write( "now it's just a matter of finding log(5) and log(3) on the calculator and substituting in the equation to solve for x. \n" ); document.write( "----- \n" ); document.write( "since log(5) = .698970004 \n" ); document.write( "and log(3) = .477121255 \n" ); document.write( "we get: \n" ); document.write( "x = .698970004 / (5*(.698970004) - .477121255) \n" ); document.write( "which becomes: \n" ); document.write( "x = .698970004 / 3.017728767 \n" ); document.write( "which becomes: \n" ); document.write( "x = .231621215 \n" ); document.write( "----- \n" ); document.write( "3^x = 3^(.231621215) = 1.289767428 \n" ); document.write( "and \n" ); document.write( "5^(5x-1) = 5^(5*(.231621215) - 1) \n" ); document.write( "which becomes: \n" ); document.write( "5^(5x-1) = 5^(.158106076) \n" ); document.write( "which becomes: \n" ); document.write( "5^(5x-1) = 1.289767428 \n" ); document.write( "which means that: \n" ); document.write( "3^x = 5^(5x-1) \n" ); document.write( "because they both = 1.289767428 \n" ); document.write( "which means that the value of x is good, and your answer is: \n" ); document.write( "x = .231621215 \n" ); document.write( " \n" ); document.write( " |