Question

Find the sum of first 17 terms of an ap whose 4th and 9th

Answer 1

Answer:

nice questions I liked it

Answer 2

Answer:

-13,600

Step-by-step explanation:

you didn't include the whole question in but i assume the 4th term is -15 and the 9th term is -30

$a_{4}=-15$

$a_{9}=-30$

$a_{4} = a+3d=-15$ (equation 1)

$a_{9}=a+8d=-30$ (equation 2)

solve linear equations and you get

a = 10

d = -5

now you just have to apply the formula to find the first few terms of an AP. which is:

$\frac{n}{2} [2a+(n-1)d]$

After applying and solving the formula you will get the answer -13,600. which is the sum of the first 17 terms of this AP.

Hope this helped and if you have any doubts just leave a comment and ill try to help you.