document.write( "Question 831708: The 11th term of an arthmetric sequence is 57 and the sum of the first and fourth terms is 29. Determine the first 3 terms of the sequence
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Algebra.Com's Answer #501602 by hovuquocan1997(83)\"\" \"About 
You can put this solution on YOUR website!
You have a formula to find any term in a arithmetic sequence and it is
\n" ); document.write( "Term = a + d(n - 1)
\n" ); document.write( "in which a is the first term and d is the difference between the terms, and n is the number of the term
\n" ); document.write( "ok so we have 11th term is 57, the equation will be
\n" ); document.write( "57 = a + d(11-1)
\n" ); document.write( "a + 10d = 57
\n" ); document.write( "That's the first equation
\n" ); document.write( "Now we move to the second one
\n" ); document.write( "We have First term is just \"a\"
\n" ); document.write( "and fourth term is a+d(4-1) = a + 3d
\n" ); document.write( "We have the sum of first and fourth terms is 29, that means a + a + 3d = 29
\n" ); document.write( "2a + 3d = 29
\n" ); document.write( "That's the second equation, now we have a system of 2 equations to solve for a, d
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Solved by pluggable solver: SOLVE linear system by SUBSTITUTION
Solve:
\n" ); document.write( " \"+system%28+%0D%0A++++1%5Ca+%2B+10%5Cd+=+57%2C%0D%0A++++2%5Ca+%2B+3%5Cd+=+29+%29%0D%0A++\"We'll use substitution. After moving 10*d to the right, we get:
\n" ); document.write( " \"1%2Aa+=+57+-+10%2Ad\", or \"a+=+57%2F1+-+10%2Ad%2F1\". Substitute that
\n" ); document.write( " into another equation:
\n" ); document.write( " \"2%2A%2857%2F1+-+10%2Ad%2F1%29+%2B+3%5Cd+=+29\" and simplify: So, we know that d=5. Since \"a+=+57%2F1+-+10%2Ad%2F1\", a=7.
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\n" ); document.write( " Answer: \"system%28+a=7%2C+d=5+%29\".
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\n" ); document.write( "\n" ); document.write( "Now you know that a = 7, meaning that the first term is 7
\n" ); document.write( "d is 5, so the second term is 12, and the third term is 17
\n" ); document.write( "So the answer is 7, 12, 17
\n" ); document.write( "TA-DAH
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