document.write( "Question 139631: The revenue R (in millions of dollars) of a large retail store can be modeled by R=1.23t^2-2.22t+8.5, where t is the number of years since 1990. Estimate the year in which the store's revenue will reach 90 million dollars?\r
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Algebra.Com's Answer #101900 by ankor@dixie-net.com(22740)\"\" \"About 
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The revenue R (in millions of dollars) of a large retail store can be modeled by R=1.23t^2-2.22t+8.5, where t is the number of years since 1990. Estimate the year in which the store's revenue will reach 90 million dollars?
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\n" ); document.write( "Replace R with 90 and solve for t
\n" ); document.write( "1.23t^2 - 2.22t + 8.5 = 90
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\n" ); document.write( "1.23t^2 - 2.22t + 8.5 - 90 = 0
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\n" ); document.write( "1.23t^2 - 2.22t - 81.5 = 0
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\n" ); document.write( "Use the quadratic formula:\"x+=+%28-b+%2B-+sqrt%28+b%5E2-4%2Aa%2Ac+%29%29%2F%282%2Aa%29+\"
\n" ); document.write( "In this equation: a=1.23, b=-2.22, c=-81.5
\n" ); document.write( "\"t+=+%28-%28-2.22%29+%2B-+sqrt%284.9284+-+4+%2A+1.23+%2A+-81.5+%29%29%2F%282%2A1.23%29+\"
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\n" ); document.write( "\"t+=+%282.22+%2B-+sqrt%284.9284+-+%28-400.98%29+%29%29%2F%282.46%29+\"
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\n" ); document.write( "\"t+=+%282.22+%2B-+sqrt%284.9284+%2B+400.98+%29%29%2F%282.46%29+\"
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\n" ); document.write( "\"t+=+%282.22+%2B-+sqrt%28405.9084+%29%29%2F%282.46%29+\"
\n" ); document.write( "Positive solution
\n" ); document.write( "\"t+=+%282.22+%2B+20.147%29%2F2.46\"
\n" ); document.write( "t = \"22.367%2F2.46\"
\n" ); document.write( "t = 9.09 ~ 9 yrs; 1999 is the year of 90 million dollars \r
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