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)\"\" \"About 
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1) x - y = 18, with x, y > 0
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\n" ); document.write( "GM is geometric mean, GM for x, y is defined as square root (x * y)
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\n" ); document.write( "HM is harmonic mean, HM for x, y is defined as 2 / (1/x + 1/y)
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\n" ); document.write( "2) 4 * square root(x * y) = 5 * (2 / (1/x + 1/y))
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\n" ); document.write( "solve equation 1) for x
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\n" ); document.write( "x = y + 18
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\n" ); document.write( "substitute for x in equation 2
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\n" ); document.write( "4 * square root((y+18) * y) = 5 * (2 / (1/(y+18) + 1/y))
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\n" ); document.write( "4 * square root((y+18) * y) = 10 / (1/(y+18) + 1/y)
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\n" ); document.write( "cross multiply the fractions
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\n" ); document.write( "4 * square root((y+18) * y) * (1/(y+18) + 1/y) = 10
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\n" ); document.write( "divide both sides of = by 4
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\n" ); document.write( "square root((y+18) * y) * (1/(y+18) + 1/y) = 5/2
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\n" ); document.write( "divide both sides of = by (1/(y+18) + 1/y)
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\n" ); document.write( "square root((y+18) * y) = (5y * (y+18)) / (4 * (y+9))
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\n" ); document.write( "square both sides of the =
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\n" ); document.write( "(y+18) * y = (25y^2 * (y+18)^2) / (16 * (y+9)^2
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\n" ); document.write( "cross multiply the fractions
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\n" ); document.write( "16y * (y+18) * (y+9)^2 = 25y^2 * (y+18)^2
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\n" ); document.write( "write the left side of the = in standard form
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\n" ); document.write( "16y^4 +576y^3 +6480y^2 +23328y = 25y^2 * (y+18)^2
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\n" ); document.write( "write the right side of the = in standard form
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\n" ); document.write( "16y^4 +576y^3 +6480y^2 +23328y = 25y^4 +900y^3 +8100y^2
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\n" ); document.write( "consolidate the terms to the left side of =
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\n" ); document.write( "-9y^4 -324y^3 -1620y^2 +23328y = 0
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\n" ); document.write( "this factors into
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\n" ); document.write( "-9y * (y-6) * (y+18) * (y+24) = 0
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\n" ); document.write( "divide both sides of = by -9
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\n" ); document.write( "our solutions for y are 0, 6, -18, -24
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\n" ); document.write( "we reject solutions 0, -18, -24 since y > 0
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\n" ); document.write( "x = 6 + 18 = 24
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\n" ); document.write( "x = 24 and y = 6
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