Question

solve 8 number......!!!!!!​

Answer 1

Answer:

your answer is 630

use formula n/2(a+l) if last number is known.

elseSum of first n terms of an AP: S =(n/2)[2a + (n- 1)d]

Step-by-step explanation:

it is actually in ap the common difference is 5

Answer 2

$\huge\boxed{\fcolorbox{white}{pink}{Answer}}$

Given:-

$\Large\boxed{</strong><strong>a</strong><strong>_</strong><strong>n</strong><strong>=</strong><strong>5</strong><strong>n</strong><strong>+</strong><strong>4</strong><strong>}$

for a1,

n = 1

$\Large\boxed{a_1=9}$

therefore,

for a15 ,

n = 15

$\Large\boxed{a_{15}=79}$

As we know that,

$\Large\boxed{S_n=n/2[a+l]}$

Sn = 15 / 2 ( 88)

Sn = 15 × 44

$\Large\boxed{S_n=660}$

Hope this helps uh..!! bro ☺️❤️