Find the value of n, if 2+5+8+11+14+.. To n terns = 610
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Number of terms = 20
Values increasing by 3. Stop at 59.
Answered by
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Answer:
a = 2
d = 3
Sn = 610
n = ?
Sn = n/2 (2a+ (n-1) ×d)
610 = n/2 (2×2+ (n-1) ×3)
610 × 2 = n (4+ 3n-3)
1220 = + 3n²- n
1220 = 3n²-n
3n²-n-1220 = 0
3n²+60n-61n - 1220 = 0
3n( n +20) - 61( n + 20)
(3n-61) ( n+20) = 0
n =-20
n =61/3
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