Question

B1=-4 bn+1=2×bn Найти b7, s7

Answer 1

раз bn + 1 = 2bn то q = 2 и по формуле bn=b1*q^(n-1) имеем b7 = 4 * 2^6 = 256

Answer 2

To find the values of b7 and s7, we need to first determine the value of b1 and then use the recursive relationship to find the subsequent terms.

Given: B1 = -4, bn+1 = 2 * bn

Step 1: Find b2 b2 = 2 * b1 b2 = 2 * (-4) b2 = -8

Step 2: Find b3 b3 = 2 * b2 b3 = 2 * (-8) b3 = -16

Step 3: Find b4 b4 = 2 * b3 b4 = 2 * (-16) b4 = -32

Step 4: Find b5 b5 = 2 * b4 b5 = 2 * (-32) b5 = -64

Step 5: Find b6 b6 = 2 * b5 b6 = 2 * (-64) b6 = -128

Step 6: Find b7 b7 = 2 * b6 b7 = 2 * (-128) b7 = -256

Now, let's calculate the sum s7, which is the sum of the first seven terms (b1 to b7):

s7 = b1 + b2 + b3 + b4 + b5 + b6 + b7 s7 = (-4) + (-8) + (-16) + (-32) + (-64) + (-128) + (-256) s7 = -4 - 8 - 16 - 32 - 64 - 128 - 256 s7 = -508

So, the value of b7 is -256, and the sum s7 is -508.