find the sum of the last term of an AP 8,10,12......126
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Answered by
2
Sn = n/2(2a+(n-1)d)
where a=8
d=2
=n/2(16+2n-2)
=n/2(14+2n)
=14n+2n²/2
=7n+n²
Sn=n²+7n
leyamahesh24:
wrong answer!!!!!!!!
Answered by
2
126= 8 + (n-1) ×2
n-1=(126-8)÷2
n=59+1=60
therefore,
Sum S= n/2 [2a + (n-1)d]
S= 60/2 [2×8 + (60-1)×2]=30×(16+118) = 30×134=4020
n-1=(126-8)÷2
n=59+1=60
therefore,
Sum S= n/2 [2a + (n-1)d]
S= 60/2 [2×8 + (60-1)×2]=30×(16+118) = 30×134=4020
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