Respuesta :
its a arithmetic progression with d = 1-3 = -1-1= -2
hence a15 = a1 + 14d
hence a15 = 3 + 14(-2) = -25
here a1 represent first term , d represent common difference
hence a15 = a1 + 14d
hence a15 = 3 + 14(-2) = -25
here a1 represent first term , d represent common difference