Question

Find the sum of the arithmetic series given a1

Answer 1

It’s B trust me I know

Answer 2

Answer:

D

Step-by-step explanation:

The sum to n terms of an arithmetic series is

$S_{n}$ = $\frac{n}{2}$ [ 2a₁ + (n - 1)d ]

where a₁ is the first term and d the common difference

Here a₁ = 12, d = 4 and n = 30 , then

$S_{30}$ = $\frac{30}{2}$ [ (2 × 12) + (29 × 4) ]

     = 15(24 + 116)

     = 15 × 140

     = 2100 → D