Question

find the sum first 12 terms an A.P. whose nth term is 5n+2

Answer 1

using formula of sum of terms
=n/2(a+An)
where a is first term of AP
and An is the last term of A.P
and n are the number of terms

the sum of first 12 terms of A.P = 414 answer

I hope you like my answer

Answer 2

a1= 2+5=7
a2 =2+10=12
d=5
a=7
S=12/2(14+11×5)
S=12/2×{69)
answer = 414