Question

7. Find the sum of 12 terms whose nth term is given by An = 3n+4​

Answer 1

Answer:

Sum of First 12 terms is 282.

Step-by-step explanation:

$A_n} =3n+4$

$A_{1}=3(1)+4 = 7$

$A_{2}=3(2)+4=10$

$d=10-7=3$

$a=7$

$n=12$

Sum of A.P = $\frac{n}{2} (2a+(n-1)d)$

                   = $\frac{12}{2}(2(7)+(12-1)3)$

                   = $6(2(7)+(11)3)$

                   = $6(14+33)$

                   = $6(47)$

                   = $282$