Question 1041057
 Find a1 if d = 4, a20 = 82, and S20 = 880. 
A.) 2 
B.) 4 
C.) 6 
D.) 60 
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an = a1+(n-1)d 
Sn = (n/2)(a1+an) 
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a(20) = a(1) + 19*4 = a(1) + 76 = 82
a(1) = 82-76 = 6
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S(20) = (20/2)(a(1) + a(20)) = 10(a(1) + 82)) = 880
a(1) + 82 = 88
a(1) = 6
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Cheers,
Stan H.
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