the 14th term of an ap is twice that the term the 6th term is minus 8 find the find the sum of its 20 term
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Answer:
-340
Step-by-step explanation:
a+ 13 d = 2(a+7d)
a + 13d = 2a + 14d
-a -d = 0
a+ d = 0 = a2 ---- --------> 1
a + 5d = -8 -----> 2
2-1
a + 5d = -8
a +. d = 0
------------------
a = 2
D = -2
a 20 = 2+ 19*-2
= -36
S20 = 10(2+(-36))
= -340
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