document.write( "Question 1088849: Write the first four terms of an arithmetic sequence whose ninth term is -51 and whose fourth term is -1. \n" ); document.write( "
Algebra.Com's Answer #703162 by rothauserc(4718)\"\" \"About 
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a(9) = -51 = a(1) + d * (9-1)
\n" ); document.write( "1) -51 = a(1) + 8d
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\n" ); document.write( "a(4) = -1 = a(1) + d * (4-1)
\n" ); document.write( "2) -1 = a(1) + 3d
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\n" ); document.write( "we have two equations in two unknowns
\n" ); document.write( ":
\n" ); document.write( "1) a(1) + 8d = -51
\n" ); document.write( "2) a(1) + 3d = -1
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\n" ); document.write( "subtract equation 2) from equation 1)
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\n" ); document.write( "5d = -50
\n" ); document.write( "d = -10
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\n" ); document.write( "substitute for d in equation 1
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\n" ); document.write( "a(1) + 8(-10) = -51
\n" ); document.write( "a(1) -80 = -51
\n" ); document.write( "a(1) = 29
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\n" ); document.write( "a(n) = 29 -10 * (n-1)
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\n" ); document.write( "the first four terms are
\n" ); document.write( "29, 19, 9, -1
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