If nth term of the A.P is 3-4n, then sum of first 20 terms of the A.P is
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here it's given that a n is equal to 3-4n
from that we get,
a= -1 and d = -4
from these,
sum of first 20 terms
=20/2[2a+{20-1}d]
=10[(2×-1)+(19×-4)]
=10[-2+(-76)]
=10[-78]
=(-780)
therefore the sum of first 20 terms is equal to (-780)
hope you understand this
pls brainliest
Answered by
1
Answer:
here it's given that a n is equal to 3-4n
from that we get,
a= -1 and d = -4
from these,
sum of first 20 terms
=20/2[2a+{20-1}d]
=10[(2×-1)+(19×-4)]
=10[-2+(-76)]
=10[-78]
=(-780)
therefore the sum of first 20 terms is equal to (-780)
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