document.write( "Question 843561: Solve each equation. Show all your work. Round your answers to four decimal places.
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document.write( "a. 63x = 104
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document.write( "b. log3(x + 2) + log3(4x – 1) = 5
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Algebra.Com's Answer #508234 by Theo(13342)![]() ![]() You can put this solution on YOUR website! 63x = 104 \n" ); document.write( "divide both sides of this equation by 63 to get: \n" ); document.write( "x = 104/63\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "log3(x+2) + log3(4x-1) = 5 \n" ); document.write( "use the log property of log(a) + log(b) = log(a*b) to get: \n" ); document.write( "log3((x+2)*(4x-1)) = 5 \n" ); document.write( "simplify the expression within the log to get: \n" ); document.write( "log3(4x^2 + 7x - 2) = 5 \n" ); document.write( "the basic property of logs states that logb(x) = y if and only if b^y = x \n" ); document.write( "apply this property to the equation to get: \n" ); document.write( "3^5 = 4x^2 + 7x - 2 \n" ); document.write( "simplify to get: \n" ); document.write( "243 = 4x^2 + 7x - 2 \n" ); document.write( "subtract 243 from both sides of this equation to get: \n" ); document.write( "0 = 4x^2 + 7x - 245 \n" ); document.write( "commute this equation to get: \n" ); document.write( "4x^2 + 7x - 245 = 0 \n" ); document.write( "factor this equation by using the quadratic formula to get: \n" ); document.write( "x = (-7 +/- sqrt(3969)) / 8. \n" ); document.write( "this simplifies to: \n" ); document.write( "x = (-7 +/- 63) / 8 \n" ); document.write( "your solutions are: \n" ); document.write( "x = 7 \n" ); document.write( "x = -8.75\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "since you can't take the log of a negative number, the solution of x = -8.75 is not good. \n" ); document.write( "the only solution left is x = 7.\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "you would need to confirm this solution is good by replacing x with 7 in the original equation to see if the equation is true.\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "the original equation is: \n" ); document.write( "log3(x+2) + log(3(4x-1) = 5 \n" ); document.write( "replace x with 7 and simplify to get: \n" ); document.write( "log3(9) + log3(27) = 5\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "log3(9) = y if and only if 3^y = 9 \n" ); document.write( "this makes y = 2, so log3(9) = 2\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "similarly, log3(27) = y if and only if 3^6 = 27 \n" ); document.write( "this makes y = 3, so log3(27) = 3\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "your equation of: \n" ); document.write( "log3(9) + log3(27) = 5 becomes: \n" ); document.write( "2 + 3 = 5 which is true.\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "this confirms the solution is good. \n" ); document.write( "x = 7 is your solution.\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( " \n" ); document.write( " |