document.write( "Question 1091579: The difference between two positive numbers is 18 and 4 times their GM is equal to 5 times their HM find the numbers \n" ); document.write( "
Algebra.Com's Answer #705993 by rothauserc(4718)![]() ![]() You can put this solution on YOUR website! 1) x - y = 18, with x, y > 0 \n" ); document.write( ": \n" ); document.write( "GM is geometric mean, GM for x, y is defined as square root (x * y) \n" ); document.write( ": \n" ); document.write( "HM is harmonic mean, HM for x, y is defined as 2 / (1/x + 1/y) \n" ); document.write( ": \n" ); document.write( "2) 4 * square root(x * y) = 5 * (2 / (1/x + 1/y)) \n" ); document.write( ": \n" ); document.write( "solve equation 1) for x \n" ); document.write( ": \n" ); document.write( "x = y + 18 \n" ); document.write( ": \n" ); document.write( "substitute for x in equation 2 \n" ); document.write( ": \n" ); document.write( "4 * square root((y+18) * y) = 5 * (2 / (1/(y+18) + 1/y)) \n" ); document.write( ": \n" ); document.write( "4 * square root((y+18) * y) = 10 / (1/(y+18) + 1/y) \n" ); document.write( ": \n" ); document.write( "cross multiply the fractions \n" ); document.write( ": \n" ); document.write( "4 * square root((y+18) * y) * (1/(y+18) + 1/y) = 10 \n" ); document.write( ": \n" ); document.write( "divide both sides of = by 4 \n" ); document.write( ": \n" ); document.write( "square root((y+18) * y) * (1/(y+18) + 1/y) = 5/2 \n" ); document.write( ": \n" ); document.write( "divide both sides of = by (1/(y+18) + 1/y) \n" ); document.write( ": \n" ); document.write( "square root((y+18) * y) = (5y * (y+18)) / (4 * (y+9)) \n" ); document.write( ": \n" ); document.write( "square both sides of the = \n" ); document.write( ": \n" ); document.write( "(y+18) * y = (25y^2 * (y+18)^2) / (16 * (y+9)^2 \n" ); document.write( ": \n" ); document.write( "cross multiply the fractions \n" ); document.write( ": \n" ); document.write( "16y * (y+18) * (y+9)^2 = 25y^2 * (y+18)^2 \n" ); document.write( ": \n" ); document.write( "write the left side of the = in standard form \n" ); document.write( ": \n" ); document.write( "16y^4 +576y^3 +6480y^2 +23328y = 25y^2 * (y+18)^2 \n" ); document.write( ": \n" ); document.write( "write the right side of the = in standard form \n" ); document.write( ": \n" ); document.write( "16y^4 +576y^3 +6480y^2 +23328y = 25y^4 +900y^3 +8100y^2 \n" ); document.write( ": \n" ); document.write( "consolidate the terms to the left side of = \n" ); document.write( ": \n" ); document.write( "-9y^4 -324y^3 -1620y^2 +23328y = 0 \n" ); document.write( ": \n" ); document.write( "this factors into \n" ); document.write( ": \n" ); document.write( "-9y * (y-6) * (y+18) * (y+24) = 0 \n" ); document.write( ": \n" ); document.write( "divide both sides of = by -9 \n" ); document.write( ": \n" ); document.write( "our solutions for y are 0, 6, -18, -24 \n" ); document.write( ": \n" ); document.write( "we reject solutions 0, -18, -24 since y > 0 \n" ); document.write( ": \n" ); document.write( "x = 6 + 18 = 24 \n" ); document.write( ": \n" ); document.write( "******************************************* \n" ); document.write( "x = 24 and y = 6 \n" ); document.write( "******************************************* \n" ); document.write( ": \n" ); document.write( " \n" ); document.write( " |