document.write( "Question 1196201: \r\n" );
document.write( "Suppose x is a positive number such that
\r. There is a unique choice of whole numbers p and q so that
. Find p+q.\r\n" );
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document.write( "My attempt:\r\n" );
document.write( "I know that if
, then
, which simplifies to
. Then what?\r\n" );
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Algebra.Com's Answer #828940 by ikleyn(52798)![]() ![]() You can put this solution on YOUR website! .\r \n" ); document.write( " \n" ); document.write( " \n" ); document.write( "\n" ); document.write( " It is VERY nice problem, admitting BEATIFUL solution.\r \n" ); document.write( "\n" ); document.write( " See below.\r \n" ); document.write( " \n" ); document.write( " \n" ); document.write( "\n" ); document.write( " \r\n" ); document.write( "If x^2 = 1-x, then\r\n" ); document.write( "\r\n" ); document.write( " x^8 = (1-x)^4 = 1 - 4x + 6x^2 - 4x^3 + x^4.\r\n" ); document.write( "\r\n" ); document.write( "\r\n" ); document.write( "The idea is to replace in this expression, and in all expressions that follow, x^2 by (1-x) \r\n" ); document.write( "everywhere, where it is possible, and as many times as possible, until you get the desired \r\n" ); document.write( "expression of degree 1 (one).\r\n" ); document.write( "\r\n" ); document.write( "\r\n" ); document.write( " See how it works\r\n" ); document.write( "\r\n" ); document.write( "\r\n" ); document.write( " x^8 = 1 - 4x + [6(1-x)] - [4x*(1-x)] + [(1-x)*(1-x)] = I continue =\r\n" ); document.write( "\r\n" ); document.write( " = 1 - 4x + 6 - 6x - 4x + 4x^2 + 1 - 2x + x^2 = 8 - 14x + 5x^2 = I replace x^2 by (1-x) again = \r\n" ); document.write( "\r\n" ); document.write( " = 8 - 14x + 5*(1-x) = 8 - 16x + 5 - 5x = 13 - 21x. \r\n" ); document.write( "\r\n" ); document.write( " \r\n" ); document.write( " So, p = 13, q = 21 and p + q = 13 + 21 = 34. ANSWER\r\n" ); document.write( "\r \n" ); document.write( "\n" ); document.write( "Solved.\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "This method is called \" the lowering of a degree \" method.\r \n" ); document.write( " \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "//////////////\r \n" ); document.write( " \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "It can be solved by different methods, but this one is a \" true delight \".\r \n" ); document.write( " \n" ); document.write( " \n" ); document.write( "\n" ); document.write( " \n" ); document.write( " |