Calculate the sum of the first 42 terms in the sequence. -10, 2, 14, 26,

17,661

Step-by-step explanation:

-10, 2, 14, 26

T1 = a = -10

T2 = 2

T3 = 14

T4 = 26

Lets find the common difference

T2 - T1 = T3 - T2

2 - (-10) = 12 = 14 - 2 = 12

common difference d = 12

therefore, this is an arithmetic progression

Sum of first 42 terms

S42 = n/2 [2a + (n - 1) * d]

where n = 42

slot in the values

S42 = 42/2 [2*(-10) + (42 -1)* 12]

S42 = 21[ -20 + (41*12)]

S42 = 21 ( -20 + 861)

S42 = 21( 841)

S42 = 17,661