In an A. P. the sum of first 10 terms is -150 and the sum of its next 10 terms is -550. Find the A. P
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Answer:
-292/3,-266/3,-80,-214/3,-188/3..........
Step-by-step explanation:
s₁₀=-150
10/2[2a+9d]=-150
5[2a+9d]=-150
2a+9d=-30...(1)
s₁₅=-550
15/2[2a+14d]=-550
15/2×2[a+7d]=-550
a+7d=-110/3....(2)
a=-110/3-7d
substituting the value of a in (1)
2(-110/3-7d)+9d=-30
-220/3-14d+9d=-30
-5d=130/3
d=26/3
now,
a=-110/3-7×26/3
=-110/3-182/3
=-110-182/3
=-292/3
so,
A.P= -292/3,-266/3,-80,-214/3,-188/3..........
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