1)Дана геометрическая прогрессия {bn}.Вычислите b3 ,если b1=2,q=-1/2 2)Дана геометрическая прогрессия {bn}.Вычислите

1) b3 - ? .

• b1 = 2 .

q = -0.5.

b3 = 2 * (-0.5) ^ (2) = 2 * 0.25 = 0.5.

2) b3 - ? .

b1 = -2.

q = -0.5.

b3 = -2 * (-0.5) ^ (2) = -2 * 0.25 = -0.5.

3) S2 - ? .

b3 = 1/3  .

q = -1/3 .

b3 = b1 * q2 .

1/3 = b1 * (-1/3) ^ (2) .

1/3 = b1 * 1/9 | * 9 .

3 = b1.

S2 = (3((-1/3) ^ (2) - 1)) / ((-1/3) -1) = (3 *(1/9) - 1) / (-4/3) = (3 * (-8/9)) / (-4/3) = (-8/3) / (-4/3) = (-8) / (-4) = 2.

S2 = 2.