Answer:
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
