3rd term of an AP is 8 ,9th term of AP exceeds 3 times the 3rd term. Find the sum
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Step-by-step explanation:
A3= 8
A9=3a3
A+ 2d= 8
A + 8d= 3(8)
= 24
A+ 2d+6d=24
8+ 6d=24
6d=16
d= 8/3
A+2(8/3)=8
A=8/3
An= n/2[2a+ (n-1) d]
=n/2[2(8/3)+ (n-1) 8/3]
= n [ 8/3+4/3n -4/3]
=n[4n/3+4/3]
= 4n^2/3 + 4n/3
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