if nth term of an ap is an is equals to 2 - 3n and find the sum of 20 terms of an AP
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1
sigma an = 2×20 - 3 (20)(21)/2
= 40 - 630
= -590
= 40 - 630
= -590
vs30988oug8ky:
nooo my question is Find the sum if first 20 terms of this AP
but here sum if the term will be used na
Answered by
2
2-3n=a +(n-1)d
= -1 +(n-1)(-3)
a= -1 ,d=-3
S20=10[2*(-1) +19×(-3)]
= 10[-2-57]
=10×(-59)
= - 590
= -1 +(n-1)(-3)
a= -1 ,d=-3
S20=10[2*(-1) +19×(-3)]
= 10[-2-57]
=10×(-59)
= - 590
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