А) 8(-7)-11(-3)=-23;
8(-3/4)-11*0,6=7,2
б)5*0-4*12=-48
5(-1,2)-4*3,25=-19
1, 2, 3, ..., 150
a1 = 1
a2 = 2
d = a2 - a1 = 2 - 1 = 1
a150 = 150
S150 = (a1 +a150)*75 = 151*75 = 11325
По определению геометрической прогрессии:
bn = b1•qⁿ-¹
b3 = b1•q²
b1 = b3/q²
b1 = 2/6² = 2/36 = 1/18
b8 = b1•q^7
b8 = 1/18•6^7 = 15552.