find the sum of first 20 terms of an AP an=3-4n?
pls it's urgent
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brilliant answer Kar dena ok bhai
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sona8845:
bhayya thnx
brilliant kar de bhai plz
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hi bro, it's me ad714 to answer you.
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
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
Attachments:
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