document.write( "Question 1087018: find the formula for a_n if a_1 = -4 and a_5 = 16. This is AP \n" ); document.write( "

Algebra.Com's Answer #701289 by ikleyn(52781) $\"\"$ $\"About$

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document.write( " =  = -4 + 4*d = 16  ====>  4d = 20  ===>  d = 5.\r\n" );
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document.write( "The formula is  = -4 + 5*(n-1) = -4 +5n - 5 = -9 + 5n,  n = 1, 2, 3, . . . \r\n" );
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document.write( "Answer. The general formula is   = -4 + 5*(n-1)  or  (which is the same)   =  -9 + 5n,  n = 1, 2, 3, . . .\r\n" );
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