By applying basic property of Geometric progression we can say that sum of 15 terms of a sequence whose first three terms are 5, -10 and 2 is $\sum_{n=4}^{15} 5(-2)^{n-1}$$$

<h3>What is sequence ?</h3>

Sequence is collection of numbers with some pattern .

Given sequence

$a_{1}=5\\\\a_{2}=-10\\\\\\a_{3}=20$

We can see that

$\frac{a_1}{a_2}=\frac{-10}{5}=-2\\$

and

$\frac{a_2}{a_3}=\frac{20}{-10}=-2\\$

Hence we can say that given sequence is Geometric progression whose first term is 5 and common ratio is -2

Now $n^{th}$ term of this Geometric progression can be written as

$T_{n}= 5\times(-2)^{n-1}$

So summation of 15 terms can be written as

$\sum_{n=4}^{15} T_{n}\\\\$\\$\sum_{n=4}^{15} 5(-2)^{n-1}$$$

By applying basic property of Geometric progression we can say that sum of 15 terms of a sequence whose first three terms are 5, -10 and 2 is $\sum_{n=4}^{15} 5(-2)^{n-1}$$$

To learn more about Geometric progression visit : brainly.com/question/14320920

8 0

3 years ago

Please help!! <br> Will mark and star!!

Kamila [148]

The answer is B. please mark me as brainlyest.

3 0

3 years ago

The longest fingernails ever recorded were 8.650 meters. How long were the fingernails in a feet and inches?

Oksana_A [137]

Answer: 28 feet and 4.5 inches

8 meters = 26.24...

.650 meters = 25 inches.

25 inches = 2 feet 1 inch

28 and 4.5 inches is your answer.

4 0

3 years ago

1. Melissa went to lunch with two friends. She purchased 3 corn dogs, 2 fruit cups, and

Lena [83]

Answer:

14 is the answer.

Step-by-step explanation:

7 0

3 years ago