(iii) The first term of an A.P.is - 5 and the 6th term is 45. Find S6
Answers
Answered by
2
Answer:
sum of first 6th term is 420
Answered by
6
Answer:
120
Step-by-step explanation:
Given that :
a = -5, T6 = 45
As we know that :
Tn = a + (n - 1)d
=> T6 = -5 + (6 - 1)d
=> 45 = -5 + 5d
=> 5d = 45 + 5
=> 5d = 50
=> d = 10
Also we know that :
Sn = n/2[ 2a + (n - 1)d ]
=> S6 = 6/2[ 2×(-5) + (6-1)10 ]
=> S6 = 3[ -10 + 50 ]
=> S6 = 3 × 40 = 120
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