Question 5.7.9: Determining the Sum of a Geometric Sequence Determine the su......

In this sequence, a_1 = 4, r = 2, and n = 5. Substituting these values into the formula, we get

s_n = \frac{a_1(1   –   r^n)}{1  –  r}

s_5 = \frac{4[1  –  (2)^5 ]}{1  –  2}

= \frac{4(1  –  32)}{-1}

= \frac{4(-31)}{-1} = \frac{-124}{-1} = 124

The sum of the first five terms of the sequence is 124. The first five terms of the sequence are 4, 8, 16, 32, 64. If you add these five numbers, you will obtain the sum 124.