Respuesta :

Term 1 = 6*1 - 12
Term 1 = 6 - 12
Term 1 = - 6

Term 14 = 6*14 - 12
Term 14 = 84 - 12
Term 14 = 72

Number of terms = 14

Sum = (term1 + Term14)*number of terms / 2
Sum  = (-6 + 72)*14/2
Sum = 66*14/2
Sum = 462