Question

if the sum of n terms of an AP is 3n²+3n,, find the rth term of an AP

Answer 1

$sum = \frac{(2a - d)n + d {n}^{2} }{2} = 3{n}^{2} + 3n \\ \: comparing \\ \frac{d}{2} = 3 \\ d = 6 \\ 2a - 6 = 6 \\ a = 6 \\ rth \: term = 6 + (r - 1)6 \\ = 6 + 6r - 6 \\ = 6r$

Answer 2

HEY MATE!!
Here Is your Answer!!
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sum=(2a-d)n+dn²/2=3n²+3n
d/2=3
d=6
2a-6=6
a=6
rth term=6+(r-1)6
=6+6r-6
=6r
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Hope It helps You!!