Find the sum 1+ 2/3+ 1/3+ 0+...... to 19 terms.
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Step-by-step explanation:
a= 1 d= -1/3 n =19
Sn = n/2[ 2a + (n- 1) d]
S19 = 19/2 [ 2× 1 + (19 -1) (-1/3)]
= 19/2 [ 2 + (18)×(-1/3)]
= 19/2 [ 2+ (-6)]
= 19/2 × - 4
= -38
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