Question

in an ap 18,13,8,3,........S35=​

Answer 1

Answer:

Step-by-step explanation:

a=18, d= -5.

S35= a+34d= 18+34(-5)= -152.

Answer 2

Answer: - 18,13,8,3, ..........S35 = -152 or -2345

Detailed solution: -

Given: -

AP is

18,13,8,3, ........S35

So,

Here a = 18 (the first term of the AP)

d = $13-18$

d = $-5$

d = -5 (the difference between the ap)

n = 35 (the number of term)

Therefore,

Using the formula $a_{n} = a+(n-1)d$, we can find the solution.

So,

$a_{n} = a+(n-1)d\\ S35 = 18+(35-1)-5\\S35 = 18+34(-5)\\S35 = 18-170\\S35= -152$

Therefore,

18,13,8,3, ..............S35 = -152

OR

By using formula $a_{n} = n/2[2a+(n-1)d]$, the answer will be,

$a_{n} = n/2[2a+(n-1)d]\\S35 = 35/2[2*18+(35-1)-5]\\S35= 35/2[36+34(-5)]\\S35=35/2[36-170]\\S35=35/2*-134\\S35=35*-67\\S35=-2345$

Therefore,

S35 = -2345

To know more about the topic, go to the given links: -

https://brainly.in/question/14165772

https://brainly.in/question/40138364

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