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
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Answered by
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
Answered by
1
Answer:
Step-by-step explanation: use formula
Sn=n/2(2a+(n-1)d)
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