Question

if the AP of the first ten terms is-80and the sum of next ten term is -280then find the AP

Answer 1

let a is the first and d is the common difference of AP
a/c to question ,
S10= -80
10/2 {2a + (10-1) d}= -80
2a +9d = -16 ---------------(1)

again ,
sum of next 10 terms = -280
S20 - S10 = -280
S20 = -280 -(-80)= -200
20/2 {2a +(20-1 ) d } = -200

2a +19 d= -20 -----------------(2)

subtracting equation (2) to (1)

10d= -20-(-16)= -4

d= -2 / 5
put d = -2/5 in equation (1)

a = -16 -9 (-2/5)= -16 +18/5
= -62/5

now,
AP is ---------
-62/5 , -64/5 , -66/5 ..........

Answer 2

Answer:

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