Question

In an AP the sum of the first 10 terms is -150 and the sum of it's next 10 terms is -550 find ap

Answer 1

Answer:

3, -1, -5, -9...........

Step-by-step explanation:

according to the question

a+(a+d)+(a+2d)+..........+(a+9d) = -150

i.e 10a+45d= -150 ----->(1

and also we know that

(a+10d)+(a+11d)+..........+(a+19d) = -550

i.e 10a+145d= -550 ------>(2

from one and 2

100d= -400

it gives d=-4

to find a put the value of d in equation one and 2

10a+45(-4) = -150

10a= 180-150

10a= 30

a=3

the ap will be

3, -1, -5, -9 and so on

Answer 2

Answer:

Step-by-step explanation: use formula

Sn=n/2(2a+(n-1)d)