Question

The common ratio of a geometric series is \dfrac14 4 1 ​ start fraction, 1, divided by, 4, end fraction and the sum of the first 444 terms is 170170170.

Answer 1

Answer:

The common ratio of a geometric series is \dfrac14

4

1 ​

start fraction, 1, divided by, 4, end fraction and the sum of the first 4 terms is 170

The first term is 128

Step-by-step explanation:

The common ratio of the geometric series is given as:

$r = \frac{1}{4}$

The sum of the first 4 term is 170.

The sum of first n terms of a geometric sequence is given b;

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

common ratio, n=4 and equate to 170.

$\frac{a_1(1-( \frac{1}{4} )^4)}{1- \frac{1}{4} } = 170$

$\frac{a_1(1- \frac{1}{256} )}{ \frac{3}{4} } = 170\\\\ \frac{255}{256} a_1 = \frac{3}{4} \times 170\\\\\frac{255}{256} a_1 = \frac{255}{2} \\\\\frac{1}{256} a_1 = \frac{1}{2} \\\\ a_1 = \frac{1}{2} \times 256\\\\a_1 = \frac{1}{2} \times 256 \\\\= 128$