document.write( "Question 898387: Solve the equation. Use a calculator to obtain decimal approximations, correct to two decimal places.\r
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document.write( "ln (2x+3)+ln(x-6)-2lnx = 0\r
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document.write( "I know the answer is 10.68 but im just not sure how my teacher got it. Any help would be appreciated. Thank you. \n" );
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Algebra.Com's Answer #544811 by Theo(13342) You can put this solution on YOUR website! your equation is:\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "ln(2x+3) + ln(x-6) - 2*ln(x) = 0\r \n" ); document.write( " \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "since ln(2x+3) + ln(x-6) = ln((2x+3) * (x-6)), your equation becomes:\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "ln((2x+3)*(x-6)) - 2*ln(x) = 0\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "since 2*ln(x) = ln(x^2) and since ln((2x+3)*(x-6)) - ln(x^2) = ln((2x+3)*(x-6)/x^2), your equation becomes:\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "ln((2x+3)*(x-6)/x^2) = 0\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "this is true if and only if:\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "e^0 = (2x+3)*(x-6) / x^2\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "since e^0 = 1, your equation becomes:\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "1 = (2x+3)*(x-6) / x^2\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "multiply both sides of this equation by x^2 and simplify to get:\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "x^2 = 2x^2 - 12x + 3x - 18 = 2x^2 - 9x - 18\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "subtract x^2 from both sides of this equation to get:\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "0 = x^2 - 9x - 18\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "factor this equation using the quadratic formula to get:\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "x = 10.68465... or x = -1.68465...\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "since x has to be positive, the solution is x = 10.68465... which rounds to 10.68.\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( " \n" ); document.write( " |