Question

Помогите ,умоляю! Срочно!

Answer 1

1) -25, -22
a_1 = -25
a_2 = -25 + 3 = -22
a_n = a_(n-1) + 3
a_21 = a_20 + 3 = a_19 + 2*3 = a_1 + 20*3 = -25 + 60 = 35

Answer 2

3) a1 = -3,1, a2 = -3,1 + 0,9; a19 = -3,1 + 18*0,9 = 13,1

Answer 3

S19 = (a1 + a19)*19/2 = (-3,1 + 13,1)*19/2 = 95